Abstract:
The present invention provides a drive mechanism for a form, fill and seal machine for forming a tube out of a heat sealable sheet. The machine includes front and rear jaw assemblies arranged on opposite sides of the tube, which follow the movement of the tube during the sealing operation. The drive mechanism for each side of the jaw assemblies comprises a front drive gear and a real drive gear, which are driven in opposing directions. The front and rear drive gears are coupled to front and rear linkage bases, respectively, which in turn are coupled to the front and rear jaw assemblies, respectively, to cyclically bring the opposing jaw assemblies into contact to seal the tube. A slide bar may be disposed directly between the front and rear linkage bases, or alternatively, directly between the front and rear jaw assemblies, to help maintain the linkage bases and jaw assemblies in registry during their rotational cycles, thereby improving the sealing quality of the package being formed.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a packaging apparatus and a method of forming packages. More specifically, the invention relates to a vertical form, fill and seal machine in which the film material is fed downwardly and cross-sealing jaws move downwardly during the sealing operation and are synchronized with the film and the package being formed. 
       BACKGROUND INFORMATION 
       [0002]    Machines for forming, filling and sealing packages from a continuous film are widely used in the packaging industry. Basic form, fill and seal (FFS) machines can be adapted to form packages of different shapes and sizes. A conventional machine may utilize a supply of packaging film, which is drawn over a forming means to achieve a tubular shape. The tubular film then may be sealed vertically using, a seam sealing machine. The contents are inserted into the package and the package may be closed using a sealing mechanism designed to seal upper and lower regions of the package. The filled and sealed package then is cut from the film roll. 
         [0003]    The cross-sealing mechanism, which seals the top and bottom of each package, is a critical component of the FFS machine insofar as controlling the quality of the package. Various designs have been proposed for a cross-sealing mechanism, but many of the designs have drawbacks. For example, known cross-sealing mechanisms may not operate at a precise time in the package cycle, thereby yielding a reduced quality seal. 
         [0004]    Further, many current cross-sealing mechanisms are complex and require significant monitoring and adjustment to assure the quality of the finished product. An intermittent or discontinuous movement of the Film and the tubular package formed therefrom introduces problems in maintaining control over the film and complicates the film feeding mechanism. For at least these reasons, there is a need for a cross-sealing mechanism that performs the sealing and cutting operations while moving vertically in time with the vertical movement of the package being formed. 
         [0005]    One particular FFS machine in which the cross-sealing jaws move downwardly during the sealing operation is disclosed in U.S. Pat. No. 5.752,370 to Linkiewicz (“the &#39;370 patent”), assigned to Triangle Package Machinery, Inc., the same assignee as for the present application. In the &#39;370 patent, a drive mechanism for forming a tube out of a heat sealable sheet is disclosed. The FFS machine comprises first and second cyclically movable jaw assemblies arranged on opposite sides of the tube, which follow the movement of the tube during the sealing operation. 
         [0006]    In the &#39;370 patent, the drive mechanism for each side of the jaw assemblies comprises five gears, i.e., ten gears total are employed. On each side, a driver gear meshes with and drives an upper rear drive gear and a lower rear drive gear in counterclockwise directions. The upper rear drive gear and lower rear drive gear mesh with and drive an upper front drive gear and a lower front drive gear, respectively, in clockwise directions. The upper and lower rear drive gears are coupled to a rear linkage base, which in turn is coupled to the rear sealing jaw using two parallel links. This mechanism causes the rear sealing jaw to move in a counterclockwise direction. Similarly, the upper and lower front drive gears are coupled to the front sealing jaw, which rotates in a clockwise direction. As the tube is fed downwardly, the front and rear sealing jaws engage the tube for a portion of their cycle to seal the tube. A plurality of pressure devices, such as rubber torsion mounts, may be employed to bias the pair of cyclically movable jaw assemblies toward each other in arcuate paths to yield an improved seal. 
         [0007]    Despite the advantages of the design in the &#39;370 patent, there is a need for an improved FFS machine that is cost-effective, utilizes fewer components, is easy to maintain and service, and still provides high quality sealing capabilities in the finished product. 
       SUMMARY 
       [0008]    The present invention provides a drive mechanism for a FFS machine for forming a tube Out of a heat sealable sheet. The FFS machine includes front and rear jaw assemblies arranged on opposite sides of the tube, which follow the movement of the tube during the sealing operation. The drive mechanism for each side of the jaw assemblies comprises a front drive gear and a rear drive gear, which are driven in opposing directions. 
         [0009]    A front linkage base is operably coupled between the front drive gear and the front jaw assembly to rotate the front jaw assembly in the same direction as the front drive gear. Similarly, a rear linkage base is operably coupled between the rear drive gear and the rear jaw assembly to rotate the rear jaw assembly in the same direction as the rear drive gear. In effect, the front and rear sealing jaws are cyclically rotated in opposing directions and engage a tube in synchronous fashion to seal the tube. 
         [0010]    In a preferred embodiment, four parallel links, each having upper and lower regions, are employed to couple the linkage bases to the jaw assemblies. Specifically, the lower regions of first and second parallel links are coupled to the front linkage base, while their upper regions are operably coupled to the front jaw assembly. Similarly, the lower regions of third and fourth parallel links are coupled to the rear linkage base, while their upper regions are operably coupled to the rear jaw assembly. The parallel links may employ mount members having pressure devices, which function to bias the front and rear jaw assemblies towards engagement, thereby enhancing the sealing capabilities of the FFS machine. 
         [0011]    In a first embodiment, a slide bar is disposed between the front linkage base and the rear linkage base to keep these linkage bases in registry with one another, thereby improving the sealing quality of the package being formed. The front and rear linkage bases may be attached to front and rear linkage housings, each having bores disposed therethrough. The slide bar extends longitudinally through the bores of the front and real linkage housings to guide the linkage bases. 
         [0012]    In an alternative embodiment, the slide bar is disposed directly between the front and rear jaw assemblies to keep the jaw assemblies in registry. The front and rear jaw assemblies preferably comprise bores disposed therethrough. The slide bar extends longitudinally through the bores to maintain the sealing jaws in registry throughout their rotational cycle. During the cycle, the slide bar may move vertically along a vertical rod, as necessary. 
         [0013]    Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be within the scope of the invention, and be encompassed by the following claims. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention can be better understood with reference to tile following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views. 
           [0015]      FIG. 1  is a left side schematic view of a sealing jaw mechanism provided in accordance with a first embodiment. 
           [0016]      FIG. 2  is a schematic view that illustrates movement of a sealing jaw during a rotational cycle. 
           [0017]      FIG. 3  is a perspective view of the sealing jaw mechanism of  FIG. 1  as shown from the front upper right. 
           [0018]      FIG. 4  is a top view of the sealing jaw mechanism of  FIG. 3 . 
           [0019]      FIG. 5  is a front end view of the sealing jaw mechanism of  FIG. 3 . 
           [0020]      FIG. 6  is a perspective view of an alternative sealing jaw mechanism as shown from the front upper right. 
           [0021]      FIG. 7  is a top view of the sealing jaw mechanism of  FIG. 6 . 
           [0022]      FIG. 8  is a front end view of the sealing jaw mechanism of  FIG. 6 . 
           [0023]      FIG. 9  is a perspective view of the sealing jaw mechanism of  FIG. 6  as shown from the front upper left. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    The present invention relates generally to a drive mechanism for a FFS machine. The FFS machine utilizes transverse sealing jaws to form sealed bags from a continuous film of packaging material. During operation, vacuum belts engage the packaging material and pull it off a mandrel. The film is fed to a seam sealing station and is sealed longitudinally by a stationary seam sealer. The film is thereby formed into a tube, which is next fed to a transverse sealing station. The transverse sealing station comprises a sealing jaw mechanism, which is described in greater detail below. 
         [0025]    Generally speaking, the sealing jaw mechanism seals the upper and lower surfaces of the package to be formed. The sealing jaw mechanism comprises front and rear jaw assemblies arranged on opposite sides of the tube, which follow the movement of the tube during the sealing operation. As the tube is fed vertically through the sealing jaws, the front and rear jaws are rotated together in synchronous motion and come into contact for a portion of their cycle to seal the tube. 
         [0026]    Referring now to  FIGS. 1-5 , a first embodiment of a drive mechanism for a FFS machine is shown. Sealing jaw mechanism  120  comprises left gear case  122  and right gear case  124 , as shown in  FIG. 3 . Left gear case  122  includes driver gear  160 , which is carried by input shaft  126  (see  FIG. 1 ). Input shaft  126  is coupled to servo motor  132  by gear box  130 , as shown in  FIG. 3 . The speed of driver gear  160  is identical to the speed of a driver gear (not shown) housed in right gear case  124  and coupled to servo motor  132  by input shaft  128 . Therefore, as will be explained in greater detail below, the left and right portions of the drive assembly of sealing jaw mechanism  120  are synchronized. 
         [0027]    It should be noted that left gear case  122  and right gear case  124 , along with their respective components that are coupled to front and rear sealing jaws  140  and  150 , are mirror images of each other. For this reason, reference will be made to  FIGS. 1-5  for a detailed discussion of the drive from left gear case  122  to the various components on the left half of assembly  120  that are coupled to front and rear sealing jaws  140  and  150 . 
         [0028]    In  FIG. 1 , a schematic of the operation of sealing jaw mechanism  120  is shown. Driver gear  160  of left gear case  122  rotates in a clockwise direction. Driver gear  160  meshes with and drives rear drive gear  162  in a counterclockwise direction. Front drive gear  161  meshes with rear drive gear  162 , and therefore front drive gear  161  is driven in a clockwise direction, as depicted in  FIG. 1 . Ultimately, as will be explained in greater detail below, the rotation of front drive gear  161  and rear drive gear  162  causes front sealing jaw assembly  142  to rotate in a clockwise direction and causes rear sealing jaw assembly  152  to rotate in a counterclockwise direction, thereby providing the sealing functionality of the FFS machine. 
         [0029]    Front drive gear  161  is operably coupled to front linkage base  155  and causes rotation of front linkage base  155  in a clockwise direction. In a preferred embodiment, front drive gear  161  is attached to output shaft  171 , which is coupled to crank arm  176   a , which in turn is coupled to front linkage base  155  at pivot shaft  178   a , as shown in  FIG. 1 . 
         [0030]    Similarly, rear drive gear  162  is attached to Output shaft  172 , which is coupled to crank arm  176   b , which in turn is coupled to rear linkage base  156  at pivot shaft  178   b . Therefore, rear drive gear  162  causes counter-clockwise rotation of rear linkage base  156 . 
         [0031]    Sealing jaw mechanism  120  preferably further comprises parallel links  181 ,  182 ,  183  and  184 . First and second parallel links  181  and  182  couple front linkage base  155  to front jaw assembly  142 , while third and fourth parallel links  183  and  184  couple rear linkage base  156  to rear jaw assembly  152 , as depicted in  FIG. 1 . Specifically, the lower ends of first and second parallel links  181  and  182  are coupled to front linkage base  155  by mount members  191   a  and  192   a , respectively, as shown in  FIG. 1 . Similarly, the lower ends of third and fourth parallel links  183  and  184  are coupled to rear linkage base  156  by mount member  193   a  and  194   a , respectively. 
         [0032]    The upper ends of first and second parallel links  181  and  182  are coupled to front jaw assembly  142 , which carries front sealing jaw  140 , by mount members  191   b  and  192   b , respectively, as shown in  FIG. 1 . Similarly, the upper ends of third and fourth parallel links  183  and  183  are coupled to rear-jaw assembly  152 , which carries rear sealing jaw  150 , by mount members  193   b  and  194   b , respectively. 
         [0033]    The mount members used to couple both the upper and lower ends of parallel links  181 - 184  preferably have circular openings formed therein, within which pressure devices are mounted. More preferably, the pressure devices may include a plurality of elastic members or rubber torsion mounts  523 , as explained with reference to  FIGS. 29-30  of the &#39;370 patent, which is hereby incorporated by reference in its entirety. Such pressure devices function to bias the front and rear jaw assemblies toward each other in arcuate paths. If employed, the sealing time in which front sealing jaw  140  engages rear sealing jaw  150  may be increased. 
         [0034]    In the embodiment of  FIGS. 1-5 , left slide bar  135  is used to maintain the orientation of front linkage base  155  with rear linkage base  156 . Similarly, right slide bar  136  is employed to maintain the orientation of symmetrical linkage bases driven through right gear case  124 , as shown in  FIGS. 4-5 . 
         [0035]    In a preferred embodiment, the upper end of front linkage base  155  is attached to front linkage housing  185 , while the upper end of rear linkage base  156  is attached to rear linkage housing  186 , as best shown in  FIGS. 1 ,  3  and  5 . Front and rear linkage housings  185  and  186  may be separate components that are welded to upper surfaces of front and rear linkage bases  155  and  156 , respectively, or alternatively, may be integrally formed with the linkage bases during manufacture. 
         [0036]    Front and rear linkage housings  185  and  186  each comprise a bore formed longitudinally therethrough. At least one bushing  195  preferably is disposed partially or fully within the bores, as shown in  FIGS. 3 and 5 . Left slide bar  135  preferably comprises an outer diameter that is slightly smaller than an inner diameter provided by bushings  195 , thereby permitting front and rear linkage housings  185  and  186  to slide longitudinally over left slide bar  135 . 
         [0037]    Specifically, as front linkage base  155  and rear linkage base  156  are driven in clockwise and counterclockwise directions, respectively, front and rear linkage housings  185  and  186  may slide longitudinally over left slide bar  135 , which may move vertically with the rotating components. Since left and right slide bars  135  and  136  maintain the front and rear linkage bases in registry, symmetrical rotation and front and rear sealing jaw assemblies  142  and  152  may be achieved. 
         [0038]    It should be noted that, in the schematic of  FIG. 1 , the initial contact of front and rear sealing jaws  140  and  150  is depicted, while in the illustrations of  FIGS. 3-5 , front and rear sealing jaws  140  and  150  are not engaged. 
         [0039]    The rotational motion of rear sealing jaws  150  is depicted in  FIG. 2 . During a cycle, initial contact between front and rear sealing jaws  140  and  150  occurs at point  146 , which is about  54  degrees above horizontal, as shown in  FIG. 2 . Rear sealing jaw  150  moves vertically downwardly along cord  147  after initial contact with front sealing jaw  140  to point  148 , which is about 54 degrees below horizontal. At point  148 , rear sealing jaw  150  intersects the circular arc that it normally follows. As a result, front and rear sealing jaws  140  and  150  travel vertically downwardly for a total arc of about 108 degrees, which is about 30% of the total mechanical cycle. 
         [0040]    Initial engagement of front and rear sealing jaws  140  and  150  commences as both sealing jaws are moving downwardly. If pressure devices Such as rubber torsion mounts are employed, as noted above, it may ensure that the sealing jaws remain engaged under pressure and move vertically downwardly during the entire sealing phase. 
         [0041]    As will be apparent, the speed of servo motor  132  is set by a microprocessor controller during the sealing phase such that the downward movement of front and rear sealing jaws  140  and  150  is synchronized with the downward movement of the tubular container being formed. In operation, after the film is sealed longitudinally by the stationary seam sealer and formed into a tube, the tube is fed vertically through front and real sealing jaws  140  and  150 . When front and rear sealing jaws  140  and  150  are brought into engagement for a portion of their cycle, the upper and lower surfaces of the package are sealed. A cutting knife (not shown) may be employed to cut the tipper and lower Surfaces of the package. 
         [0042]    It will be appreciated that while four parallel links  181 - 184  are depicted in the embodiment of  FIGS. 1-5 , fewer links may be employed. For example, a first parallel link may be used to couple front linkage base  155  to front jaw assembly  142 , while a second parallel link may be used to couple rear linkage base  156  to rear jaw assembly  152 . If only one parallel link is employed for each linkage base, then the parallel links may be thicker or comprise a different configuration than shown in  FIGS. 1-5 . Alternatively, parallel links  181 - 184  may be omitted entirely and front and rear linkage bases  155  and  156  may be coupled directly to front and rear jaw assemblies  142  and  152 , respectively. 
         [0043]    Referring no to  FIGS. 6-9 , an alternative embodiment is described. In  FIGS. 6-9 , alternative sealing jaw mechanism  220  is similar to sealing jaw mechanism  120  of  FIGS. 1-5 , but comprises a different drive mechanism, as explained below. 
         [0044]    Like the embodiment above, it should be noted that the components on the left half of sealing jaw mechanism  220 , which are coupled to front and rear sealing jaws  240  and  250 , are mirror images of the components on the right half of mechanism  220 . Therefore, reference will only be made in  FIGS. 6-9  to a detailed discussion of the various components on the left half of sealing jaw mechanism  220 . 
         [0045]    In  FIG. 6 , output shafts  271  and  272  are driven by front drive gear  261  and rear drive gear  262 , respectively (see  FIG. 9 ). Output shafts  271  and  272  are coupled to crank arms  276   a  and  276   b , respectively. Crank arms  276   a  and  276   b  are coupled to front and rear linkage bases  255  and  256 , respectively, at pivot shafts. In effect, clockwise rotation of front drive gear  261  causes clockwise rotation of front linkage base  255  through the output shaft and the crank arm. Similarly, counterclockwise rotation of rear drive gear  262  causes counterclockwise rotation of rear linkage base  256 . 
         [0046]    In a preferred embodiment, first and second parallel links  281  and  282  interconnect front linkage base  255  with front jaw assembly  242 , while third and fourth parallel links  283  and  284  interconnect rear linkage base  256  with rear jaw assembly  252 , as explained above with respect to the embodiment of  FIGS. 1-5 . Preferably, the upper and lower regions of parallel links  281 - 284  employ mount members, which may comprise pressure devices that function to bias the pair of jaw assemblies toward each other in arcuate paths. 
         [0047]    In the embodiment of  FIGS. 6-9 . Left slide bar  235  is coupled directly between front jaw assembly  242  and rear jaw assembly  252 . Preferably, left slide bar  235  comprises an outer diameter that is slightly smaller than an inner diameter of bores formed in front and rear jaw assemblies  242  and  252 , as depicted in  FIGS. 6-9 , thereby permitting the jaw assemblies to slide longitudinally over left slide bar  235 . Similarly, right slide bar  236  is employed so that the mirror-image components on the right side of front and rear jaw assemblies  242  and  252  may slide over right slide bar  236 . 
         [0048]    As shown in  FIG. 9 , left slide bar  235  is coupled to left vertical rod  265  by slidable bracket  267 . Left slide bar  235  is attached to a front portion of slidable bracket  267 . A rear portion of slidable bracket  267  comprises a bore formed therein. Left vertical rod  265  is disposed through the bore formed in slidable bracket  267  to permit the bracket to slide vertically along the rod. Left vertical rod  265  is attached to rigid frame  269 , as shown in  FIG. 9 . Similarly, right vertical rod  266  is employed so that right slide bar  236  may move vertically over vertical rod  266  via slidable bracket  268 . 
         [0049]    In operation, as front sealing jaw  240  and rear sealing jaw  250  rotate clockwise and counterclockwise, respectively, front and rear jaw assemblies  242  and  252  slide longitudinally over left slide bar  235  and right slide bar  236  to maintain the sealing jaws in registry throughout their rotational cycle. During the cycle, slidable bracket  267  may move vertically along left vertical rod  265 , while slidable bracket  268  may move vertically along right vertical rod  266 , as necessary. It should be noted that the orientation of front and rear linkage bases  255  and  256  are maintained by the slide bars acting through front and rear jaw assemblies  242  and  252  and parallel links  281 - 284 . 
         [0050]    The bores formed in front and rear jaw assemblies  242  and  252  may comprise bushings  295 , as depicted in  FIGS. 6-7  and described above, or another type of guide means for facilitating longitudinal movement of the jaw assemblies along the slide bars. 
         [0051]    It will be apparent that in the embodiment of  FIGS. 6-9 , fewer links may be employed. For example, as noted above with respect to the embodiment of  FIGS. 1-5 , only one parallel link may be used to couple each linkage base to its respective jaw assembly, or alternatively, each linkage base may be coupled directly to a front or rear portion of the jaw assembly. 
         [0052]    While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.