Patent Publication Number: US-6214113-B1

Title: Gumming device

Description:
This application is a continuation of copending application International Application PCT/IT99/00223 filed on Jul. 16, 1999 and which designated the U.S., claims the benefit thereof and incorporates the same by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a gumming device. 
     The present invention is especially suitable for gumming sheet material on a packing machine, to which the following description refers purely by way of example. 
     BACKGROUND ART 
     Known units for gumming sheet material normally feature mechanical, and in particular roller or spray, gum applying devices, which, though highly efficient, involve several drawbacks. 
     In particular, roller devices operate at relatively slow speed, well below the requirements of modern machinery, particularly modern packing machines, and, by featuring a gumming roller rotating partly immersed in a bath of gum, are particularly “dirty” and therefore require frequent cleaning. Moreover, during machine stoppages, the bath of gum tends to dry by remaining in contact with the air with no provision for stirring the gum. 
     On the other hand, spray devices are relatively expensive and unreliable, due to frequent clogging of the spray nozzles. 
     DISCLOSURE OF INVENTION 
     It is an object of the present invention to provide a gumming device designed to eliminate the aforementioned drawbacks, and which, in particular, is straightforward in design and cheap to produce, while at the same time permitting fast, accurate gumming. 
     According to the present invention, there is provided a gumming device comprising two disks coaxial with each other and of equal diameter; a central cavity defined between the two disks; supply means for feeding gum under pressure to said central cavity; and drive means for rotating said two disks synchronously and continuously about their axis; said two disks defining, in between, an outlet opening for the gum; and said outlet opening extending along at least one portion of an outer circumference of said two disks. 
    
    
     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: 
     FIGS. 1 and 2 show two lateral sections of a preferred embodiment of the gumming device according to the present invention in two different operating configurations; 
     FIG. 3 shows a larger-scale lateral section of two instants in the operation of a detail in FIG. 1; 
     FIG. 4 shows a larger-scale front view, with parts removed for clarity, of a further detail in FIG. 1; 
     FIG. 5 shows a view in perspective, sectioned along line V—V in FIG. 4, of part of the FIG. 1 gumming device. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Number  1  in FIG. 1 indicates as a whole a gumming device for depositing liquid gum  2  onto a blank  3  fed along a path P on a known packing machine (not shown). 
     Gumming device  1  comprises an inner disk  4  and an outer disk  5  of equal diameter, which are fitted coaxially with each other to a frame  6  and are rotated synchronously and continuously about a central axis  7  by a drive device  8 . 
     A central cavity  9  is defined between disks  4  and  5 , communicates on one side with a device  10  for supplying gum  2  at a given pressure along a channel  11  extending along axis  7 , and communicates externally on the other side through at least one outlet opening  12  for gum  2 . In the example shown, openings  12  are two in number, are defined between disks  4  and  5 , and each extend along a respective portion of an outer circumference  13  of disks  4  and  5 . 
     Disks  4  and  5  are mounted to slide with respect to each other along axis  7 , and are connected to an actuating device  14  for varying the width A (FIG. 3) of openings  12  between a zero closed value and a given maximum open value by varying the distance between disks  4  and  5  along axis  7 . 
     As shown in FIG. 4, inner disk  4  supports two annular seals  15 , which are located in diametrically opposite positions on the surface of disk  4  facing disk  5  to limit openings  12  to respective given diametrically opposite portions of outer circumference  13 . 
     As shown in FIG. 3 a , each outlet opening  12  is defined by the outlet end of a respective channel  16  communicating at one end with the outside and at the other end with central cavity  9 , and which comprises a constant-section first portion  17  communicating with central cavity  9 , and a second portion  18  communicating with portion  17  and with the outside and having an outwardly increasing section. 
     Disks  4  and  5  comprise respective lateral surfaces  19  and  20 , which are substantially cylindrical, are coaxial with each other and with axis  7 , define, in between and together with seals  15 , the two openings  12 , and act as a support, in use, for blank  3 . 
     As shown in FIG. 1, disk  4  is fitted to a hollow shaft  21  having an inner conduit  22  communicating with central cavity  9 ; and disk  5  is fitted to a shaft  23  housed coaxially inside shaft  21  to define, inside conduit  22 , annular-section channel  11  for supplying gum  2  to central cavity  9 . 
     Frame  6  supports a cylindrical body  24 , which is fitted to frame  6  coaxially with axis  7 , has a central hole  25 , and is fitted to frame  6  so as to slide along axis  7  and with respect to frame  6  under the control of an actuating device (not shown). Shaft  21  is inserted inside hole  25 , and is supported by body  24  by means of a pair of thrust ball bearings  26  so as to rotate about axis  7  in an axially-fixed position with respect to body  24 . 
     Shaft  23  projects from shaft  21  via the interposition of a sealing element  27 , which is located at the opposite end  28  of conduit  22  to that communicating with central cavity  9 , enables shaft  23  to slide with respect to shaft  21 , and prevents gum  2  from issuing from the opposite end of channel  11  to cavity  9 . 
     Drive device  8  comprises a ring gear  29 , which is fitted coaxially about shaft  21 , is fitted to shaft  21  by means of a key  30 , and is held in place by a ring nut  31  screwed to a threaded outer portion  32  of shaft  21 . Drive device  8  also comprises a gear  33 , which is located with its axis (not shown) parallel to axis  7 , is connected in axially-sliding manner to ring gear  29 , and is rotated at constant speed by a known motor (not shown). 
     Device  10  for supplying gum  2  comprises an annular distributor  34 , in which is defined an annular inner cavity  35  communicating, along a conduit  36 , with a pump  37  for drawing gum  2  from a tank  38 . Distributor  34  and cavity  35  are fitted through with shaft  21 , which is mounted to rotate with respect to distributor  34 ; two annular sealing elements  39  are fitted to distributor  34  and connected to shaft  21  to seal cavity  35  and prevent gum  2  from leaking along the outer periphery of shaft  21 ; and shaft  21  has a transverse through hole  40  formed through the portion of shaft  21  surrounded by cavity  35  to connect cavity  35  permanently to channel  11 . 
     Actuating device  14  exerts axial thrust on shaft  23 , in opposition to an elastic element  41 , to move shaft  23  axially with respect to shaft  21 ; and elastic element  41  transmits a drive torque from shaft  21  to shaft  23  to rotate shaft  23  synchronously with shaft  21 , and normally maintains disks  4  and  5  in a closed position corresponding to a zero width A of openings  12 . 
     Actuating device  14  comprises a push rod  42 , which is movable along axis  7  and connected to one end  43  of shaft  23 ; and elastic element  41  comprises a spring  44 , which is wound coaxially about shaft  23  and compressed between one end  45  of shaft  21  and an annular stop body  46  integral with end  43  of shaft  23 . 
     Actuating device  14  also comprises a sensor  47  for detecting the pressure value at which gum  2  is supplied to central cavity  9 ; a sensor  48  for detecting the rotation speed value of disks  4  and  5 ; a sensor  49  for detecting the temperature value of gum  2 ; and a control unit  50  connected to sensors  47 ,  48 ,  49  and for adjusting width A of openings  12  as a function of the above values. 
     A cylindrical cavity  51  is defined, coaxially with axis  7 , in frame  6  to house disks  4  and  5 ; and said actuating device (not shown) provides for moving body  24  (and hence disks  4  and  5 ), distributor  34  and push rod  42  synchronously along axis  7  between a withdrawn rest position (FIG. 2) in which disks  4  and  5  are housed inside cavity  51 , and an extracted work position (FIG. 1) in which disks  4  and  5  are located outside cavity  51  and along the path P of blank  3 . 
     Operation of gumming device  1  will now be described with particular reference to FIG. 1, and as of the instant in which disks  4  and  5  are set to said closed position corresponding to said zero width A of openings  12 . 
     In connection with the above, it should be pointed out that disks  4  and  5  are normally maintained in the closed position when gumming device  1  is idle, so as to isolate the gum  2  in cavity  9  from the outside atmosphere. 
     To begin with, drive device  8  rotates shaft  21 , and hence shaft  23  angularly integral with shaft  21 , at substantially constant angular speed; and, at the same time, pump  37  feeds gum  2  under pressure to cavity  35  and through hole  40  and along channel  11  to central cavity  9 . 
     Actuating device  14  then moves push rod  42  along axis  7  to move disk  5  axially with respect to disk  4  and increase the width A of each opening  12  to a given value greater than zero and depending on the pressure and temperature of gum  2 , and on the speed of shafts  21  and  23 , i.e. of disks  4  and  5 . 
     As shown in FIG. 3 b , the centrifugal force produced by disks  4  and  5  rotating continuously about axis  7 , and the supply pressure exerted by pump  37  cause gum  2  to flow along channel  16  to each opening  12 , outside which a drop of gum  2  is formed due to capillarity and adhesion of gum  2  to the facing surfaces of disks  4  and  5 . 
     As blank  3  is fed along path P, the gum  2  emitted as described above from each opening  12  is brought into contact with and deposited onto a surface  52  of blank  3 . 
     By virtue of the two seals  15 , gumming device  1  provides for gumming surface  52  of, blank  3  along a discontinuous line. 
     Width A of each opening  12  is regulated by control unit  50  as a function of the pressure and temperature of gum  2  and the speed of shafts  21  and  23 , i.e. of disks  4  and  5 , so as to Feed opening  12  with a substantially constant amount of gum. 
     As shown in FIG. 1, surfaces  19  and  20  of disks  4  and  5  may act as a supporting spindle by which to fold blank  3  along a bend line  53  in the course of the above gumming operations. 
     In an alternative embodiment not shown, frame  6  supports a known cleaning device for removing any leftover gum  2  from surfaces  19  and  20  and from the outer surface of portion  18  of channel  16  once the gumming operations are completed. In one embodiment not shown, the cleaning device comprises a rod with one end shaped to fit between disks  4  and  5 , which, as they rotate with respect to the rod, provide for removing any leftover gum. 
     In an alternative embodiment not shown, the cleaning device comprises a water spray nozzle for removing any leftover gum by directing a jet of water between disks  4  and  5 . 
     Said cleaning devices may cooperate with disks  4  and  5  in either the withdrawn rest position or the extracted work position.