Abstract:
An assembly and method for forming bags ( 10 ) having a “block bottom” with external flanges ( 13 ). The method and apparatus includes forming folds ( 18 ) in a strip ( 17 ) and delivering the strip ( 17 ) to a former ( 30 ) so that the folds ( 18 ) engage the forming surface ( 33 ) to thereby locate the flanges ( 18 ) on the exterior of the tubular bag material ( 32 ).

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to packaging machines and more particularly to apparatus that deliver to packaging machines strip material which is formed into bags by the packaging machine.  
       BACKGROUND OF THE INVENTION  
       [0002]     One form of packaging includes a bag of generally of square or rectangular configuration having flanges at each longitudinal corner. Typically such bags have a “block bottom” so that they stand upright with the flanges extending upwardly.  
         [0003]     Machinery that produces the above discussed bags are intermittent in motion. More particularly, the flanges are formed by halting movement of the film and welding the flanges while the film is stationary.  
         [0004]     The above discussed apparatus have a number of disadvantages including slow operation as the dwell time for the welding process is time consuming. A further disadvantage is the complexity of the machinery and problems associated with the heaters that form the welds. A still further problem is that frequently the seals in these bags fail as product dropping into the bags ruptures the flanges.  
         [0005]     In the above mentioned apparatus it should be noted that the bag material is formed into a tube and then subsequently formed so as to have longitudinally extending flanges. Accordingly, the flanges are formed downstream (after) the bag material has passed the former.  
         [0006]     Described in UK Patent Application 2357991 is a bag in which folds are disposed inwardly of the bag to reinforce the bag. A folding apparatus forms folds in the strip bag material, with the folded strip bag material being delivered to a former so that the folds are located internally of the former and do not engage the forming surface of the former. The bags so formed have the disadvantage of reduced area available for printing. A still further disadvantage is that the folds project inwardly of the former and can inhibit the delivery of product to the interior of the tubular bag material. When forming bags with longitudinal flanges, correctly locating the flanges is difficult. This problem is exacerbated when the flanges are inside the bag material. A still further disadvantage is the problem of transversely sealing the bag material. With the folds inside the bag material the sealing jaws engage a layered construction consisting of six layers. Accordingly, the probability of a defective seal being formed is increased. This problem will be exacerbated where stripping is required as product may be difficult to move from the scaled area due to the layered construction.  
       OBJECT OF THE INVENTION  
       [0007]     It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages.  
       SUMMARY OF THE INVENTION  
       [0008]     There is disclosed herein an assembly including folding apparatus, through which strip material passes along a predetermined path to be longitudinally folded, and a former to which the strip material is delivered to font the strip material into a tube having longitudinally extending folds, the apparatus including:  
         [0009]     a plurality of transversely spaced folding slots extending generally parallel to said path and through which portions of the strip material to be folded are moved;  
         [0010]     a press member operatively associated with each slot to press each strip portion into a respective one of the slots to form a fold;  
         [0011]     a fold former associated with each slot to engage the folds passing therethrough to deform the folds so that the folds maintain their configuration; and wherein  
         [0012]     said former is operatively associated with said folding apparatus so that said folds are on the exterior of said tube.  
         [0013]     Preferably, said former has a forming surface over which the strip passes, and wherein said folds contact the former surface  
         [0014]     Preferably, each press member is of a circular configuration that rotates as it presses the strip material into the associated slot.  
         [0015]     In an alternative preferred form, each press member is a blade that extends into a respective one of the slots to press the strip material into the slot.  
         [0016]     Preferably, each fold former is a heated block having a longitudinal slot along which the folds pass to be heated there by.  
         [0017]     Preferably, each fold former further includes rollers to engage the folds to secure portions to the folds together so that the folds maintain their configuration.  
         [0018]     Preferably, the apparatus forms four generally parallel co-extensive folds.  
         [0019]     There is further disclosed herein a combination to form tubular bag material having longitudinally extending flanges, said combination including:  
         [0020]     a folding station through which strip bag material passes so as to he longitudinally folded so that the strip material leaving the station has longitudinally extending folds; and  
         [0021]     a packaging machine former, operatively associated with the folding station, to receive the bag material with the longitudinally extending folds so that the former provides tubular bag material having longitudinally extending external flanges.  
         [0022]     Preferably, said former has a forming surface that engages the strip material to form the tubular bag material, with said folding station being associated with said former so that said folds contact said former surface.  
         [0023]     Preferably, the folding station includes a plurality of transversely spaced folding slots extending generally parallel to said path and through which portions of the strip material to be folded are moved; and a press member operatively associated with each slot to press each strip portion into a respective one of the slots to form a fold.  
         [0024]     There is further disclosed herein a method of providing tubular bag material having longitudinally extending flanges, said method including the steps of:  
         [0025]     providing a supply of strip material to be used to form bags;  
         [0026]     moving the strip material from said supply and longitudinally folding the strip material so that the strip material has longitudinally extending folds; and  
         [0027]     passing the strip with folds over a packaging machine former so as to provide tubular bag material having external longitudinally extending flanges.  
         [0028]     Preferably, the former has a forming surface that contacts the folds. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]     Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings wherein:  
         [0030]      FIG. 1  is a schematic perspective view of a bag formed from flexible strip material;  
         [0031]      FIG. 2  is a schematic side elevation of an apparatus to provide film for a packaging machine which forms the bag of  FIG. 1 ;  
         [0032]      FIG. 3  is a schematic end elevation of the apparatus of  FIG. 2 ;  
         [0033]      FIG. 4  is a schematic side elevation of a modification of the apparatus of  FIG. 2 ;  
         [0034]      FIG. 5  is a schematic end elevation of the apparatus of  FIG. 4 ;  
         [0035]      FIG. 6  is a schematic top plan view of the apparatus of  FIGS. 2 and 3 ;  
         [0036]      FIG. 7  is a schematic end elevation of the strip produced by the apparatus of FIGS.  2  to  6 ; and  
         [0037]      FIG. 8  is a schematic perspective view of a packaging machine former to which the strip of  FIG. 7  is being delivered so that the former produces tubular bag material having longitudinally extending flanges. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0038]     In U.S. Pat. Nos. 4,663,917, 3,522,689, 3,070,931, 4,516,379, 3,629,987 and 4,524,567 there are various packaging machines described. These packaging machines have jaws which from discreet bags from tubular bag material. The tubular bag material is formed from strip material delivered to a former  30  ( FIG. 8 ). The strip leaving the former  30  is of a tubular configuration. Typically, the strip is plastics material and is longitudinally scaled and transversely sealed to form discreet bags. Product to be contained in the bags passes through the centre of the former  30  to be delivered to the interior of the tubular bag material.  
         [0039]     The strip material delivered to the former  30  comes from a roll.  
         [0040]     In  FIG. 1  there is a schematically depicted a bag  10 . The bag  10  has a “block bottom” in that it will stand in a stable manner on its bottom surface  11 . The bag  10  has four side panels  12  and may be of a square or rectangular transverse cross-section. Joining the side panels  12  are external flanges  13 . The upper end of the bag  10  has sloping portions  14  extending to a top seal  15 . The bag  10  also has a bottom seal  16 .  
         [0041]     The bag  10  is formed from strip material that passes through a packaging machine such as the above mentioned packaging machines.  
         [0042]     The bag  10  is formed from a strip  17  shown in end elevation in  FIG. 7 . The strip  17  has longitudinally extending folds  18  that form the external flanges  13  of the bag  10 . The strip  17  is preferably formed of plastics material. The folded strip is delivered to a packaging machine former  30  as shown in  FIG. 8 .  
         [0043]     The strip  17  is longitudinally folded at a folding station by means of a folding apparatus  20 . The apparatus  20  receives unfolded strip  19  from a roll and forms the longitudinally extending folds  18  so as to provide the strip  17 .  
         [0044]     The apparatus  20  includes a plurality of elongated members  21  each with a longitudinally extending slot  22 . Associated with each slot  22  is a relatively narrow roller  23  that projects inwardly of its associated slot  22 .  
         [0045]     The strip  19 / 18  passes along a predetermined path through the apparatus  20 . The slots  22  and form folds  18  extend parallel to the longitudinal direction of extension of the strip  17 / 19  and therefore generally parallel to the path along which the strip  17 / 19  passes.  
         [0046]     As the strip  19  approaches the slots  22  it is deflected into the slots  22  by the rollers  23 . More particularly rollers  23  rotate about a generally horizontal axis  24  that extends generally normal to the strip  17 / 19  and slots  22 .  
         [0047]     After exiting the slots  22  the strip  17  passes over heating blocks  25 . The heating blocks  25  have longitudinally extending slots  26 , each slot  26  being aligned with a respective one of the slots  22  so as to receive a respective fold  18 . As the strip  17  passes through the blocks  25 , the folds  18  are heated to a desired temperature. Upon leaving the heating blocks  25  each fold  18  is engaged by a pair of rollers  27  so that each fold  18  is compressed therebetween so that the plastics material fuses (welds) to thereby ensure that each fold  18  retains its configuration. The rollers  27  rotate about generally vertical axis  28 . The axis  28  are generally normal to the strip  17 .  
         [0048]     As is best seen in  FIGS. 2 and 3 , the rollers  23  are movable between a first position at which the rollers  23  are spaced from the slots  22 , and a second position projecting inwardly of the slots  22  to form the folds  18 .  
         [0049]     In this embodiment there are four slots  22  and four associated rollers  23  and four heating blocks  25  each having a slot  26 .  
         [0050]     In the embodiment of  FIGS. 4 and 5  the rollers  23  are replaced by blades  29 . The blades  29  are movable in the same manner as the rollers  23  but further includes a ramp surface to aid in moving the strip  19  into the slots  22 .  
         [0051]     As best seen in the accompanying drawings (particularly  FIG. 7 ) the folds  18  after being formed are subsequently engaged by rollers so that they are applied to a major surface of the strip  17 , that is they lay flat on a major surface (bottom) of the strip  17 . This facilitates movement of the strip  17  over the former of the packaging machine. The folds  18  are of a “U” shaped configuration in transverse cross-section.  
         [0052]     As best seen in  FIG. 8 , the former  30  receives the strip  17  with the longitudinally extending folds  18 . The Strip  17  passes a roller  31  to be delivered to the former  30 . The former  30  forms tubular bag material  32  having longitudinally extending external flanges  13 . In particular the folds  18  contact the former surface  33  over which the strip  17  passes to be formed into the tubular bag material  32  with the folds  18  on the exterior.  
         [0053]     In another embodiment one or more opposing pairs of heated rollers  34  are located in the block  25 . The folds  18  pass between the rollers  34  of each opposing pairs  34  to weld the folds  18  so that the folds  18  maintain their configuration.