Abstract:
A method and device for end closing tubular wrappings of products, whereby the arms of a scissor-type parting device, once inserted in a closed position inside an end portion of a tubular wrapping, are allowed to part, and are pushed by springs into a fully open position throughout an extraction stroke to crease the end portion and enable the end portion to be pressed taut and accurately by the opposing thrust of two folding-sealing members.

Description:
The present invention relates to a method of end closing tubular wrappings of products. 
   More specifically, the present invention relates to a method of end closing tubular wrappings of products, of the type comprising the steps of imparting an insertion stroke to a scissor-type parting device to insert the parting device axially inside an end portion of the tubular wrapping projecting from a corresponding end of the relative product, the parting device comprising two arms movable with respect to each other between a closed rest position and an open stretch position, and commencing said insertion stroke in the closed position; moving said arms into the open position to deform said end portion into a duckbill shape and define, on the deformed end portion, two facing, substantially flat walls; imparting an extraction stroke to said parting device to withdraw the parting device from said end portion; and gripping said end portion between two folding-sealing members to seal said walls to each other. 
   The present invention is particularly advantageous for wrapping stacks of sweets and similar, to which the following description refers purely by way of example. 
   BACKGROUND OF THE INVENTION 
   On wrapping machines, particularly for wrapping stacks of sweets and similar, in which the ends of tubular wrappings are closed using the known method described above, the scissor-type parting device is opened by means of a cam device, which moves the movable arms into the open position at a given point along the insertion stroke inside the relative end portion of the tubular wrapping for closing, and closes the movable arms at a corresponding point along the extraction stroke (the opening and closing movements, being governed as they are by the same cam device, necessarily being specular). 
   The above known method involves several drawbacks, mainly on account of the above movements imparted to the arms of the parting device. 
   In the first place, the parting device necessarily opens, during the insertion stroke, before reaching the end of the end portion to be deformed (otherwise, since the opening and closing movements are specular, the parting device would close at the same point at which it is opened, without effecting any deformation), and then proceeds in the open position until it contacts the relative end of the product, thus resulting in “crumpling” of the end portion. 
   In the second place, the parting device closes before it is fully withdrawn from the end portion being deformed, thus failing to ensure the opposite flaps of the end portion are properly taut when gripped between the folding-sealing members. 
   And finally, since the parting device closes before being fully withdrawn from the end portion, correct duckbill shaping of the outer portion of the end portion is not necessarily guaranteed. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a method of end closing tubular wrappings, designed to eliminate the aforementioned drawbacks. 
   According to the present invention, there is provided a method of end closing tubular wrappings, as claimed in Claim  1  and, preferably, in any one of the Claims depending directly and/or indirectly on Claim  1 . 
   The present invention also relates to a device for, end closing tubular wrappings. 
   According to the present invention, there is provided a device for end closing tubular wrappings, as claimed in Claim  6  and, preferably, in any one of the Claims depending directly and/or indirectly on Claim  6 . 

   
     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 plan view, with parts removed for clarity, of a preferred embodiment of the closing device according to the present invention; 
       FIG. 2  shows a section along line II—II in  FIG. 1 ; 
       FIGS. 3 and 4  show respective operating sequences of a detail in FIG.  1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Number  1  in  FIG. 1  indicates as a whole a device for end closing a tubular wrapping  2  enclosing an elongated product  3  defined, in the example shown, by a stack of sweets or similar, and having a longitudinal axis  4 . In the example shown, tubular wrapping  2  and product  3  are substantially cylindrical, but may be of any other elongated shape. Tubular wrapping  2  is formed in known manner from a sheet of heat-seal wrapping material, and comprises a central portion  5  contacting product  3 ; and two end portions  6 , each of which projects outwards with respect to a relative end surface  7  of product  3 , and must be closed to end close tubular wrapping  2 . 
   With reference to  FIGS. 1 and 2 , closing device  1  comprises two parting devices  8  located an adjustable distance apart, and facing each other along an axis  9 , which, in use, coincides with longitudinal axis  4  of product  3 . In the example shown, one of the two parting devices  8 , located at the top in FIG.  1  and indicated  8   a , is fitted to an actuating rod  10  parallel to axis  9 , and which performs a forward or insertion stroke and a return or extraction stroke in a direction  11 ; and the other parting device  8 , indicated  8   b , is fitted, so as to be adjustable axially as a function of the length of tubular wrapping  2 , to an actuating rod  12  substantially coaxial with actuating rod  10  and movable in the opposite sense to actuating rod  10  to also perform a forward or insertion stroke and a return or extraction stroke in direction  11 . 
   Each parting device  8  is a scissor-type parting device comprising a supporting block  13 , which is connected to the relative actuating rod  10 ,  12 , is defined at the top by a flat surface  14 , and is fitted through with two pins  15  and  16 , which have respective parallel axes  17 , are located side by side in a plane perpendicular to axis  9 , and are perpendicular to surface  14 . Pins  15  and  16  are fitted in rotary manner to relative block  13 , and are fitted, on top and substantially contacting surface  14 , with respective flat rocker arms  18  and  19 , preferably made of sheet metal and coplanar with each other. Underneath relative block  13 , pins  15  and  16  are fitted with respective gears  20  meshing with each other and having a 1:1 gear ratio; and pin  16  is fitted, underneath relative gear  20 , with a crank  21  perpendicular to relative axis  17  and fitted on the free end with a tappet roller  22 . 
   With reference to  FIG. 1 , each rocker arm  18 ,  19  comprises an inner arm  23 , i.e. facing the other parting device  8 , and an outer arm  24  located on opposite sides of relative axis  17 . More specifically, viewed from above, each inner arm  23  tapers towards its free end, and is defined, on the side facing the other rocker arm  19 ,  18 , by a straight edge  25 , which is positioned parallel to axis  9  and substantially contacting edge  25  of inner arm  23  of the other rocker arm  19 ,  18 , when relative parting device  8  is in the closed rest position; and, viewed from above, each outer arm  24  also tapers towards its free end, and is defined, on the side facing the other rocker arm  19 ,  18 , by a straight edge  26 , which is positioned parallel to axis  9  and substantially contacting edge  26  of outer arm  24  of the other rocker arm  19 ,  18 , when relative parting device  8  is in the fully open position. In other words, the angle by which each rocker arm  18 ,  19  rotates about relative axis  17  to pass from the closed to the fully open position equals an angle A between relative edge  26  and an extension of relative edge  25  towards relative edge  26 , and the size of which is so selected that, when relative parting device  8  is in the fully open position, the distance between the outer edges of free-end portions  27  of the two inner arms  23  equals at least “R”, where R is the radius of tubular wrapping  2  or, if tubular wrapping  2  is not cylindrical, the radius of the cylinder in which tubular wrapping  2  can be inscribed. 
   Outwards of relative rocker arms  18  and  19 , each parting device  8  comprises a U-shaped bracket  28  fitted to relative block  13 , with its concavity facing outer arms  24 , and with two opposite wings  29  located alongside and on opposite sides of arms  24  to support respective springs  30 , each of which is positioned substantially crosswise to axis  9  and compressed between relative wing  29  and the outer edge of relative outer arm  24  to keep relative rocker arm  18 ,  19  normally in the fully open position. 
   Beneath and alongside blocks  13 , there is provided a locking device  31  for locking inner arms  23  of the two parting devices  8  in the closed position. Locking device  31  comprises an actuating rod  32  parallel to axis  9  and rotating about its axis to move locking device  31 , in a direction  33  substantially crosswise to axis  9 , between a lock position contacting parting devices  8 , and a rest position detached from parting devices  8 . 
   Locking device  31  also comprises two cam members  34 , each of which is L-shaped, is associated with a relative parting device  8  to cooperate with relative tappet roller  22 , and in turn comprises a top plate  35  substantially parallel to top surface  14  of relative supporting block  13 , and having a lateral edge  36  cooperating with relative tappet roller  22 , and a bottom arm  37  extending upwards with respect to the axis of rod  32 , and rotating with rod  32  to move relative plate  35  between said lock and rest positions. More specifically, the length of edge  36  is such that, if relative plate  35  were kept permanently in the lock position, inner arms  23  of rocker arms  18  and  19  of relative parting device  8  would be kept permanently in the closed position, regardless of the position assumed by parting device  8  as it moves in direction  11  with respect to tubular wrapping  2 . 
   For each parting device  8 , closing device  1  also comprises two folding-sealing members  38 , which are indicated  38   a  and  38   b  and located respectively above and below the plane defined by relative rocker arms  18  and  19 . Folding-sealing members  38   a  and  38   b  are movable, in opposite senses in a direction  39  parallel to pins  15  and  16 , to and from a closed position gripping a relative end portion  6  of tubular wrapping  2 . 
   Operation of closing device  1  will now be described with reference, in particular, to  FIGS. 3 and 4 , and, given the identical, specular operation of parting devices  8   a  and  8   b , with reference to only one parting device indicated  8 . 
   When tubular wrapping  2 , fed crosswise to its longitudinal axis  4  by a known conveying device (not shown), is arrested with its longitudinal axis  4  coaxial with axis  9  ( FIG. 3   a ), parting device  8  is in a withdrawn rest position at the start end of its insertion stroke, with end portions  27  of inner arms  23  outside the facing end portion  6 . In this position, locking device  31  is in the  FIG. 1  lock position, and keeps the two inner arms  23  substantially contacting each other, i.e. in the closed position. 
   Parting device  8  then performs the insertion stroke in direction  11  to bring end portions  27  substantially into contact with end surface  7  of product  3  ( FIG. 3   b ); and, throughout the insertion stroke, locking device  31  remains in the  FIG. 1  lock position to keep inner arms  23  in the closed position. At this point, actuating rod  32  ( FIG. 1 ) is rotated to withdraw plate  35  from relative tappet roller  22  in direction  33 , so that inner arms  23  are rotated by springs  30  about relative axes  17  into the open position, and relative end portions  27  exert substantially constant pressure on an inner surface  40  of relative end portion  6 . 
   Parting device  8  ( FIG. 4   a ) then begins the extraction stroke, and gradually deforms end portion  6  into a duckbill shape. More specifically, during the extraction stroke, end portions  27  of inner arms  23  slide along inner surface  40  to form, on end portion  6 , two diametrically opposite crease lines, so that at least the free end of end portion  6  gradually assumes the form of two substantially flat, parallel walls  41 , which are connected along edges  42  extending along said crease lines, and are kept perfectly taut by inner arms  23  pushed constantly, throughout the extraction stroke, into the fully open position by springs  30 . The folding of end portion  6  along edges  42  is assisted by folding-sealing members  38 , which, maintained in an open position throughout the insertion stroke, are moved towards each other in direction  39  as soon as the extraction stroke starts, and are arrested in an intermediate position ( FIG. 4   a ) defining, between them, a gap  43  wide enough to loosely accommodate the two walls  41  and inner arms  23 . 
   When inner arms  23 , still pushed by springs  30  into the fully open position, withdraw completely from end portion  6  ( FIG. 4   b ), the two folding-sealing members  38  are pressed together in direction  39  to seal the two walls  41  and close the end of end portion  6 . When parting device  8  completes the extraction stroke, locking device  31  is reactivated to restore inner arms  23  to the closed position. 
   In connection with the above, it should be stressed that: inner arms  23  are only allowed to open at the end of the insertion stroke; inner arms  23  are pushed constantly into the fully open position throughout the extraction stroke and, at any rate, until they withdraw completely from end portion  6 ; and said crease lines are formed to ensure that, when sealed, walls  41  are perfectly taut and perfectly connected to each other along edges  42 .