Abstract:
A method and machine for folding and finishing training pant diapers, whereby the diapers are formed from respective flat blanks, each of which is fed to a continuously-rotating, suction-type first wheel, and is folded into a U by clamping an intermediate portion of the blank on the first wheel by means of a folding member; retaining a trailing half of the blank on the first wheel, while detaching a leading half from the first wheel by means of a continuously-rotating, suction-type second wheel; transferring the leading half to a continuously-rotating, suction-type third wheel; and gradually superimposing the leading half of the blank onto the trailing half, as the trailing half advances on the first wheel, and after first removing the folding member from the blank.

Description:
The present invention relates to a method and machine for folding and finishing training pant diapers. 
   BACKGROUND OF THE INVENTION 
   In the diaper industry, diapers are normally folded by feeding a succession of flat diapers along a linear conveyor; arresting each flat diaper with a central portion positioned over a transverse opening in the linear conveyor; and folding the diaper into a U by inserting a folding member through the opening. 
   Though widely used, by being simple and efficient, the above method has several serious drawbacks, particularly at maximum production speed, and which derive from two factors: firstly, potential damage of the diaper, given its relatively fragile structure, by the rapid in-out movement of the folding member; and, secondly, and more importantly, the impossibility, given the way in which the folding operation is performed, of promptly controlling the position of the two halves of the diaper superimposed during the folding operation, with the result that one half of the folded diaper is offset in respect of the other. 
   The problem is further compounded in the relatively recent production of so-called “training pant” diapers which, after being folded into a U in the same way as conventional diapers, are joined permanently, e.g. sealed, along the lateral portions to form a closed annular girdle enabling the diaper to be used pant-fashion. 
   While U-folding conventional diapers does not necessarily call for a high degree of precision, the same obviously does not apply to training pants, in which case, the flat diaper must be folded extremely accurately so that the lateral portions to be joined permanently overlap perfectly. 
   As stated, experience has shown that the above folding method, by failing to control the folding operation and ensure precise overlapping of the two halves of the diaper, and therefore of the portions to be joined permanently, may result in an unacceptable end product, both in terms of function and appearance. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a method of folding and finishing training pant diapers, designed to ensure extremely precise folding of the diapers, and the production of diapers which are both functionally and aesthetically satisfactory. 
   According to the present invention, there is provided a method of folding and finishing training pant diapers, as claimed in the attached Claims. 
   According to the present invention, there is also provided a machine for folding and finishing training pant diapers, as claimed in the attached Claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A number of non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which: 
       FIG. 1  shows a partial, schematic view of a first preferred embodiment of the machine according to the present invention; 
       FIG. 2  shows a partial, schematic view of a second preferred embodiment of the machine according to the present invention; 
       FIG. 3  shows a larger-scale view in perspective of a detail of  FIGS. 1 and 2 ; 
       FIGS. 4-9  show the  FIG. 1  machine in respective different operating configurations. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Number  1  in  FIGS. 1 and 2  indicates as a whole a machine for folding and finishing training pant diapers  2 , i.e. diapers shaped and closed pant-fashion, by which to train babies in the use of the corresponding undergarment. 
   More specifically, as is known, a training pant diaper  2  comprises a closed annular girdle; and a padded crotch connected to both sides of the annular girdle to define, with the girdle, two leg holes. 
   As shown in the  FIG. 1  details, each diaper  2  is formed from a respective flat, H-shaped blank  3  comprising two substantially rectangular transverse bands  4  which, when joined, define the annular girdle of diaper  2  as described above; and a longitudinal crosspiece  5  connecting bands  4  and defining the crotch of the finished diaper  2 . 
   With reference to  FIGS. 1 and 2 , machine  1  comprises a folding unit  6 , in turn comprising a main wheel  7  rotating continuously (clockwise in the drawings) about an axis  8  perpendicular to the  FIG. 1  plane; a wheel  9  which rotates continuously (anticlockwise in the drawings) about an axis  10  parallel to axis  8 , and is tangent to wheel  7  at a transfer station  11 ; and a wheel  12  which rotates continuously (anticlockwise in the drawings) about an axis  13  parallel to axes  8  and  10 , is substantially tangent to wheel  9  at a point downstream from transfer station  11  in the rotation direction of wheel  9 , and is tangent to wheel  7  at a folding station  14  for folding blanks  3  and located downstream from transfer station  11  in the rotation direction of wheel  7 . 
   Wheels  7 ,  9  and  12  are known suction wheels, and each comprise a known perforated skirt (not shown) selectively connected to a respective known suction chamber (not shown) to retain blanks  3  on relative wheel  7 ,  9 ,  12 . Blanks  3  are fed to main wheel  7  by a feed line  15 , an output portion of which is defined by a wheel  16  tangent to wheel  7 , at a point upstream from transfer station  11 , and mounted to rotate about an axis  17  parallel to axis  8 . 
   Along feed line  15 , blanks  3  are fed longitudinally in the form of a continuous strip  18  defined by a succession of blanks  3  connected at respective bands  4 . More specifically, as shown in one of the  FIG. 1  details, each band  4  of a blank  3  is connected to band  4  of the contiguous blank  3  along a respective cut line corresponding, after blank  3  is detached, to a free transverse edge  19  of band  4 . 
   For this purpose, wheel  16  is fitted with a known cutting device comprising a knife  20  which, at a cutting station  21  located at the point of tangency between wheels  7  and  16 , moves to and from wheel  7  to cut strip  18  transversely into a continuous succession of individual blanks  3 . 
   As explained in more detail below, once separated, blanks  3  are fed, starting from cutting station  21 , along a folding path extending partly about wheels  7 ,  9  and  12 , and partly coinciding with the work branches of two conveyors  22  and  23 , of which, conveyor  22  is wound about wheel  7  and a return pulley  24   a , and conveyor  23  is wound about wheel  12  and a return pulley  24   b.    
   More specifically, as shown in  FIGS. 1 and 2 , pulleys  24   a  and  24   b  rotate about respective axes parallel to axis  8 , are tangent to each other, and define, on relative conveyors  22  and  23 , respective substantially mating work branches, which extend from folding station  14  to the point of tangency between pulleys  24   a  and  24   b , and define a guide channel for the folded blanks  3  issuing from folding station  14 . Each conveyor  22 ,  23  comprises (as shown in  FIG. 3  relative to conveyor  22 ) two parallel belts, each located close to a respective free edge of relative wheel  7 ,  12  and of relative pulley  24   a ,  24   b.    
   As shown in  FIG. 1 , machine  1  also comprises a heat-sealing device  25  located at folding station  14 , and which, as explained below, provides for heat sealing the end portions of bands  4 , as each folded blank  3  travels through folding station  14 , to form the closed annular girdle of relative diaper  2 . 
   In the  FIG. 2  variation, sealing device  25  is an ultrasound sealing device which, as opposed to being located between wheels  7  and  12 , is located at a point downstream from folding station  14 , along the guide channel defined by the work branches of conveyors  22  and  23 . Also, as compared with the previous embodiment, pulleys  24   a  and  24   b  are located further away from wheels  7  and  12 , so that the respective work branches defining the guide channel of blanks  3  are longer. 
   In other embodiments, not shown, ultrasound sealing device  25  may be located at folding station  14 , and heat-sealing device  25  may be located downstream from folding station  14 , along the guide channel defined by conveyors  22  and  23 . 
   In a further variation, sealing device  25  may be replaced by a different type of connecting device for connecting bands  4  permanently or releasably, such as a glue or Velcro applicator. 
   As shown in  FIGS. 1 and 2 , and in more detail in  FIG. 3 , wheel  7  is equipped with a number of pairs of folding devices  26  fitted to wheel  7 , equally spaced about axis  8 , and each comprising two identical folding devices  26  located symmetrically on opposite sides of wheel  7 , close to the cylindrical peripheral surface of wheel  7 . 
   As shown in  FIG. 3 , each folding device  26  comprises a clamp  27  operated by an actuating device  28  to move—in time with clamp  27  of the corresponding folding device  26  and to and from the cylindrical outer surface of wheel  7 —between a raised rest position, and a lowered work position in which clamp  27  is pressed against the outer cylindrical surface of wheel  7  to clamp an intermediate portion of a relative blank  3  on wheel  7 , as explained in more detail below. 
   Actuating device  28  comprises a cam  29  fitted to the drive shaft of wheel  7 ; and a transmission which is interposed between cam  29  and clamp  27  to move clamp  27  to and from the raised rest position in response to continuous rotation of cam  29 , and in turn comprises a rocker arm  30  hinged to wheel  7  to oscillate about an axis  31  parallel to axis  8 , and having a first arm which extends from axis  31  towards cam  29  and is fitted on its free end with a roller cam follower  32  rolling on cam  29 . 
   Rocker arm  30  also comprises a second arm which extends substantially crosswise to the first arm and constitutes a crank of an oblique articulated quadrilateral comprising a connecting rod  33 , hinged to the free end of the second arm to oscillate about an axis  34  parallel to axis  31 , and a second crank defined by an arm  35 , which extends substantially crosswise to connecting rod  33  and the second arm, and is hinged to the free end of connecting rod  33  to oscillate about an axis  36  crosswise to axis  34  and sloping with respect to a radial plane through axis  8  of wheel  7 . 
   At the opposite end, arm  35  is hinged to a block  37 , integral with wheel  7 , to oscillate about an axis  38  parallel to axis  36 , and is fitted rigidly with clamp  27 . 
   Oscillation of rocker arm  30  about axis  31  is therefore converted, by connecting rod  33 , to oscillation of arm  35  about axis  38 , thus moving clamp  27  from the raised rest position to the lowered work position, or vice versa. 
   Actuating device  28  also comprises a push spring  39  compressed between rocker arm  30  and a bracket integral with wheel  7 , to keep cam follower  32  in contact with cam  29  in use. 
   Operation of machine  1  will now be described as of  FIG. 1 , and with particular reference to one blank  3  which, for the sake of clarity, is indicated hereinafter as blank  3   a.    
   In the  FIG. 1  operating configuration, blank  3   a , just cut off strip  18  by knife  20 , is located immediately downstream from cutting station  21 , is retained on wheel  7  by suction, and is positioned with its inner surface (i.e. the surface directly contacting the skin when relative diaper  2  is in use) facing outwards of wheel  7 . 
   It should be pointed out that wheel  7  and wheel  16  are so synchronized, and the number of folding devices  26  along the periphery of wheel  7  is such that, as a blank  3  is fed to wheel  7 , a pair of clamps  27  is always located at a mid-portion of blank  3 . 
   As of the  FIG. 1  position, blank  3   a  is fed by wheel  7  along the folding path until the leading edge  19  of blank  3   a  reaches transfer station  11 . 
   At this point, suction in the sector of wheel  7  immediately downstream from transfer station  11  is at least partly cut off, and suction in the sector of wheel  9  immediately downstream from transfer station  11 , in the rotation direction of wheel  9 , is activated. 
   As a result, the leading edge  19  of blank  3   a  is sucked onto wheel  9 , and, as wheels  7  and  9  rotate continuously, the leading half of blank  3   a  is detached from wheel  7  and gradually winds onto the cylindrical outer surface of wheel  9 . 
   As shown in  FIG. 4 , before the leading half of blank  3   a  is laid completely on wheel  9 , the two clamps  27  located at the mid-portion of blank  3   a  are moved by respective actuating devices  28  from the raised rest position to the lowered work position to clamp the mid-portion of blank  3   a  on wheel  7 . 
   When the leading half of blank  3   a  is wound completely on wheel  9 , and clamps  27 , in the lowered work position, have travelled through transfer station  11  ( FIG. 5 ), suction in the sector of wheel  7  immediately downstream from transfer station  11  is restored, so that the trailing half of blank  3   a  passing transfer station  11  remains firmly attached to wheel  7 . 
   At the same time, suction in the sector of wheel  9  between transfer station  11  and the point of tangency between wheel  9  and wheel  12  is cut off, so that, as the trailing half of blank  3   a  moves away from transfer station  11 , the leading half is detached easily from the surface of wheel  9 . 
   That is, since clamps  27  secure blank  3   a  firmly to wheel  7 , and the leading half must necessarily follow the trailing half, the trailing half would tear the leading half off wheel  9 , thus damaging blank  3   a , if the leading half were not sufficiently free to come away from wheel  9 . 
   However, to ensure the leading half is detached gradually from wheel  9 , as opposed to coming away completely from wheel  9  and “collapsing” onto the trailing half, suction is maintained in the portion of wheel  9  corresponding to the portion of the leading half close to edge  19  ( FIG. 6 ), and is activated in the sector of wheel  12  extending between the point of tangency with wheel  9  and folding station  14 , so that the leading half of blank  3   a , as it is detached from wheel  9 , adheres to wheel  12  and remains flat. 
   As shown in  FIG. 7 , continuous rotation of wheels  7  and  12  gradually brings the leading and trailing halves together to fold blank  3   a  into a U. And, on reaching a point immediately upstream from folding station  14 , clamps  27  are moved by actuating device  28  from the lowered work position to the raised rest position. 
   From this point on, as blank  3   a  is fed gradually through folding station  14  and then inserted, downstream from folding station  14 , between the belts of conveyors  22  and  23  ( FIGS. 8 and 9 ), the leading half and trailing half of blank  3   a  are superimposed completely. 
   With reference to the  FIG. 1  embodiment, diaper  2  is finished, i.e. the end portions of bands  4  are sealed to form the closed annular girdle, as bands  4  travel through folding station  14  and past sealing device  25 . 
   In other words, on machine  1 , each flat blank  3  is fed to folding station  14  by a first conveyor—in this case, wheel  7 ; the trailing half of each blank  3  is clamped on the first conveyor upstream from folding station  14  in the travelling direction of the first conveyor; the leading half of each blank  3  is transferred from the first conveyor to a further conveyor—in this case, wheel  12 —which cooperates with the first conveyor to fold blanks  3  into a U at folding station  14 ; and transverse bands  4  of each U-folded blank  3  are joined to form the relative closed annular girdle. 
   The leading half of each blank  3  is transferred from wheel  7  to wheel  12  via wheel  9 . However, in a variation not shown, wheel  9  may be replaced by a continuous or intermittent mechanism with or without suction. 
   Once completed, diaper  2 , gripped between the belts of conveyors  22  and  23 , is carried off folding unit  6  and fed to a known packing unit (not shown). 
   In the  FIG. 2  variation, on the other hand, the folded but as yet unsealed blank  3  is carried away from folding station  14 , between the belts of conveyors  22  and  23 , and is completed later by sealing device  25 . 
   In this connection, it should be pointed out that the two belts of each conveyor  22 ,  23  are wound about relative wheel  7 ,  12  and about relative pulley  24   a ,  24   b  at such a distance apart that, when diaper  2  is inserted between the belts downstream from folding station  14 , the belts engage the end portions of bands  4  to keep the two halves of blank  3  perfectly superimposed, and, in particular, to prevent the end portions of bands  4  from shifting with respect to each other before being sealed. 
   Also for this purpose, suction is preferably activated in a sector of wheel  12  located immediately downstream from folding station  14 , to retain the blank  3  issuing from folding station  14  firmly in contact with wheel  12 . 
   To conclude, it should be pointed out that the system for selectively activating and cutting off suction on wheels  7 ,  9  and  12  provides, at the successive transfer and folding stages, for accurate handling of blank  3 , with no sharp changes in direction, and, in particular, for continually controlling the position of blank  3  with respect to wheels  7 ,  9  and  12  to ensure, at the folding stage, precise overlapping of the two halves of blank  3  and perfect alignment of bands  4  to be sealed to form the closed annular girdle of diaper  2 .