Patent Publication Number: US-6901725-B2

Title: Method and wrapping wheel for conditioning stacks of products

Description:
The present invention relates to a wrapping method for conditioning stacks of products. 
   More specifically, the present invention relates to a wrapping method for conditioning stacks of products, of the type comprising a feed step, in which a stack of products is fed to a radial seat of a wrapping wheel rotating in steps about an axis of rotation to feed the radial seat in a given travelling direction and along an endless path extending through a stack loading station and an unloading station, the stack being positioned with its longitudinal axis parallel to said axis of rotation, and being fed to the radial seat through an output station of a feed line supplying heat-seal sheets of wrapping material, so as to mate with a respective sheet of wrapping material at said output station, and engage the relative radial seat while folding the relative sheet of wrapping material into a U with two opposite lateral flaps projecting from the relative stack and outwards of the radial seat; a first folding step, in which the two flaps are folded about the relative stack to define, about the stack, a tubular wrapping coaxial with said longitudinal axis and having a longitudinal rib defined by superimposed lateral end portions of said flaps; a sealing step, in which said lateral end portions are sealed to each other; and a second folding step, in which said rib is folded squarely onto an outer surface of the relative tubular wrapping. 
   The present invention is particularly advantageous for use on machines for wrapping stacks of sweets and similar, to which the following description refers purely by way of example. 
   BACKGROUND OF THE INVENTION 
   On known wrapping wheels, particularly for stacks of sweets, operating according to the above method, the two lateral flaps are normally folded together to form the longitudinal rib by a gripper on the relative radial seat, and are fed, so folded, to a sealing station where two opposite sealing devices grip the rib; the rib is released when the radial seat is started up again and leaves the sealing station; and the rib is folded squarely by a fixed folding member downstream from the sealing station. 
   In other words, the longitudinal rib is sealed during a stop of the relative radial seat at a sealing station, and so affects the output rate of the wrapping wheel as a whole. That is, sealing the longitudinal rib takes a relatively long time, normally longer than the follow-up folding and sealing operations performed by the wrapping wheel at other work stations, so that the stop times of the wrapping wheel must conform with those of the longest operation, thus reducing efficiency. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a wrapping method designed to eliminate the aforementioned drawback. 
   More specifically, it is an object of the present invention to perfect the above known wrapping method to minimize the stop times of the wrapping wheel. 
   According to the present invention, there is provided a wrapping method for conditioning stacks of products, 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 wrapping wheel for conditioning stacks of products. 
   According to the present invention, there is provided a wrapping wheel for conditioning stacks of products, as claimed in claim  9  and, preferably, in any one of the claims depending directly and/or indirectly on claim  9 . 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A non-limiting embodiment of the 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 preferred embodiment of the wrapping wheel according to the present invention; 
       FIG. 2  shows a larger-scale detail of  FIG. 1 ; 
       FIG. 3  shows a section along line III—III in  FIG. 2 ; 
       FIG. 4  shows a section along line IV—IV in  FIG. 2 ; 
       FIGS. 5  to  9  show the  FIG. 2  detail in successive operating positions; 
       FIG. 10  shows views in perspective of a folding sequence performed by the  FIG. 1  wrapping wheel. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Number  1  in  FIG. 1  indicates as a whole a wrapping machine for conditioning stacks  2  of sweets  3  by means of respective sheets  4  of heat-seal wrapping material. 
   Wrapping machine  1  comprises a wrapping wheel  5  fitted to a frame  1   a  to rotate (anticlockwise in the drawings) about a horizontal axis  6 , and comprising a number of peripheral radial seats  7 , which are fed in steps in a given travelling direction  8  and along an endless path P extending through a loading station  9  for loading stacks  2 , and an unloading station  10  for unloading the wrapped stacks  2 . 
   Each radial seat  7  receives a respective stack  2  positioned with a relative longitudinal axis  11  ( FIG. 10 ) parallel to axis  6 , and comprises two opposite jaws  12  and  13  for gripping a relative stack  2 , and which extend outwards from the periphery of a central disk  14  of wrapping wheel  5 . More specifically, jaw  12 , located upstream from relative jaw  13  in travelling direction  8 , is fitted to central disk  14  ( FIG. 4 ) to rotate, with respect to central disk  14 , about a relative axis  15  parallel to axis  6 , and defines the outer arm of a rocker arm  16 , an inner arm of which is fitted on the free end with a tappet roller  17  cooperating with a cam  18  ( FIGS. 7-9 ) extending about axis  6  to control oscillation of jaw  12  to and from jaw  13 , which is fixed. 
   Each stack  2  is fed to loading station  9  along a radial conduit  19  and in a radial feed direction  20  by a pusher  21  outside wrapping wheel  5 , and by a counterpusher  22  carried by a fixed central hub of wrapping wheel  5 . Pusher  21  moves through an output station  23  of a feed line  24 , supplying sheets  4  of wrapping material, to mate each stack  2  with a respective sheet  4  of wrapping material, and to push ( FIG. 6 ) the whole so formed between jaws  12  and  13  of a relative radial seat  7  arrested at loading station  9 . As each stack  2  and relative sheet  4  of wrapping material are pushed towards relative radial seat  7  arrested at loading station  9 , relative sheet  4  of wrapping material is folded into a U with its concavity facing radially outwards, and with two opposite lateral flaps  25  of sheet  4  projecting rearwards from relative stack  2 . 
   Wrapping wheel  5  has a folding gripper  26  comprising two rocker arms  27  and  28  pivoting about axis  6  and located in front of central disk  14  of wrapping wheel  5 . Rocker arm  27 , located upstream from rocker arm  28  in travelling direction  8 , comprises a work arm  29  facing loading station  9 , and defining a first jaw of folding gripper  26 ; and a control arm  30 . Rocker arm  28  comprises a work arm  31  facing loading station  9  and arm  29 , and defining a second jaw of folding gripper  26 ; and a control arm  32  overlapping arm  30 . To the free ends of arms  30  and  32  are hinged respective output connecting rods  33  and  34  of respective actuating crank mechanisms  35  and  36  comprising respective cranks  37  and  38  hinged to relative connecting rods  33  and  34  and fitted to respective drive shafts  39  and  40  coaxial with each other and with an axis  41  parallel to axis  6  and outside path P. Drive shafts  39  and  40  oscillate differently about axis  41 , as explained in detail later on, to impart oscillations to arms  29  and  31  along a portion P 1  of path P extending in travelling direction  8  from loading station  9  and along a given arc as explained in detail later on. 
   Arms  29  and  31  define the two jaws of folding gripper  26 , and, as shown in  FIGS. 2 and 3 , are fitted integrally on their free ends with respective cross members  42  and  43  extending parallel to each other, alongside central disk  14 , parallel to axis  6 , and outside path P. On the side facing cross member  42 , cross member  43  supports, in a fixed position and by means of screws  44 , a sealing rod  45  located alongside disk  14 , parallel to axis  6 , and longer than stacks  2 ; and, on the side facing cross member  43 , cross member  42  supports, in a fixed position, a U-shaped apron  46  for a sealing rod  47  facing and parallel to sealing rod  45 , and fitted with two screws  48  fitted in sliding manner through cross member  42  to enable sealing rod  47  to move crosswise to its axis towards cross member  42  in opposition to springs  49  coaxial with screws  48  and compressed between sealing rod  47  and cross member  42 . 
   In actual use, and with reference to  FIGS. 1 and 5  to  10 , when wrapping wheel  5  stops ( FIG. 1 ) with a seat  7  at loading station  9 , and with movable jaw  12  and folding gripper  26  both in the open position, a sheet  4  of wrapping material is laid across radial conduit  19  at output station  23 . At this point, counterpusher  22  moves outwards into contact with sheet  4  of wrapping material, while pusher  21  moves in direction  20  towards wrapping wheel  5  to feed a stack  2  of sweets  3  along radial conduit  19  and into contact with sheet  4  of wrapping material. Pusher  21  and counterpusher  22  then move together in direction  20  to feed the whole defined by stack  2  and relative sheet  4  of wrapping material to seat  7 . In the course of which movement, sheet  4  of wrapping material, held contacting relative stack  2  by the opposing action of pusher  21  and counterpusher  22 , is folded into a U about relative stack  2  ( FIGS. 5 and 10   b ), and is still in this position on reaching relative seat  7 . When movable jaw  12  closes (FIG.  6 ), sheet  4  is positioned inside relative seat  7  with lateral flaps  25  projecting outwards from seat  7  and between the two sealing rods  45  and  47 . 
   Before pusher  21  and counterpusher  22  part to release stack  2  inside relative seat  7 , drive shafts  39  and  40  are operated to cause folding gripper  26  to perform a relatively small first closing movement (between  FIGS. 6 and 7  and not shown) to fold lateral flaps  25  slightly about relative stack  2  (while still leaving pusher  21  free) and prevent sweets  3  from falling when pusher  21  is detached. 
   Once pusher  21  is withdrawn past output station  23 , folding gripper  26  completes the closing movement (FIG.  7 ), so that sealing rods  45  and  47  are brought into contact compressing springs  49 , and two end portions  25   a  of lateral flaps  25  are brought into contact to define ( FIG. 10   c ) a longitudinal fin or rib  50  closing a tubular wrapping  51 , which is coaxial with longitudinal axis  11  of relative stack  2 , and has two opposite ends  52  projecting outwards of respective ends of relative stack  2 . Only at this point do sealing rods  45  and  47 —which, though heated, have so far operated substantially as straightforward folding devices—begin operating as sealing devices to seal longitudinal rib  50  closing tubular wrapping  51 . 
   Wrapping wheel  5  ( FIG. 8 ) then moves in travelling direction  8  to feed seat  7  to the next work station  53 ; and drive shafts  39  and  40  are operated to keep folding gripper  26  in the closed position, while at the same time enabling folding gripper  26  to follow seat  7  along portion P 1 , which extends along an arc centred about axis  6  and generally shorter than the arc between two adjacent seats  7 . Sealing of rib  50  can thus continue downstream from loading station  9  to reduce the stop times of wrapping wheel  5 . 
   Once rib  50  is sealed, folding gripper  26  is arrested and opened to release rib  50 , which ( FIGS. 9 and 10   d ) is folded backwards onto a lateral surface  54  of relative tubular wrapping  51  on striking sealing rod  45 , which in this case acts as a fixed folding device. 
   When the wrapped stack  2  passes the end of portion P 1 , folding gripper  26 , still in the open position, is restored to its original position in FIG.  1 .