Abstract:
An apparatus for taking up imbricated bags carried by a pair of carrier tapes includes two carrier tape winding spools positioned coaxially with one another; and a differential gear unit positioned between said spools and adapted to be removably connectable to a shaft of a bag loader whereby the pair of carrier tapes can be wound up on said spools with equal tension. A method includes providing a bag train having a succession of imbricated bags on two supply tapes having lead ends equipped with two tape-winding spools with a differential gear unit positioned coaxially between the spools; connecting the differential gear unit to a shaft of said bag loader; and driving said spools to wind up said tapes on said spools with equal tension to bring each of the imbricated bags successively to a loading position where each bag is loaded and separated from the tapes.

Description:
The present application is a 35 USC §371 application of PCT/EP03/10754 filed Sep. 26, 2003, which claims the benefit of EP Patent Application No. 02256908.1 filed Oct. 3, 2002. 
   FIELD OF THE INVENTION 
   The present invention relates to an apparatus for taking up tapes on which a succession of imbricated bags, suitable for packaging, are carried. For example, meat cuts, or poultry may be loaded into the bags as they are removed from the tapes by a bag loader. 
   BACKGROUND OF THE INVENTION 
   The use of taped imbricated bags has been known for many years and the most commonly available form of these bags uses two separate adhesive carrier tapes which have an imbricated array of the bags placed on the tapes in such a way that the adhesive face of each tape contacts the exposed part of each bag in the imbricated array. Normally the lead bag of the array is attached to the tapes by its end at which the mouth is disposed. 
   U.S. Pat. No. 4,798,412 discloses a bag loader which includes a differential drive unit which drives two driving shafts onto which a cassette can be loaded. The cassette contains two tape winding spools one for each tape of a chain of bags. The differential drive unit of the bag loader can wind up the tapes onto the spools with equal tension. However, the drive unit of the bag loader is complicated and requires many components because of the two shafts which must extend from the bag loader with axes which are parallel but not coaxial. Furthermore, such a cassette is required to hold the spools in place and is necessarily quite large and bulky as the spools are positioned one beside the other to allow connection to the two shafts of the drive unit of the bag loader. 
   GB 2,064,477 discloses a bag loader which includes a differential drive unit which drives two tape winding spools which are positioned coaxially with one another. The differential drive gear is permanently attached to the bag loader (integral therewith). Thus, to load a succession of imbricated taped bags, the two used tapes need to be removed from the spools by an operator who also needs to connect the new tapes to the same empty spools in the bag loader. 
   SUMMARY OF THE INVENTION 
   The present invention provides an apparatus for taking up a succession of imbricated packaging bags carried by a pair of carrier tapes, said apparatus comprising: two carrier tape winding spools positioned coaxially with one another; and a differential gear unit positioned between said spools, said differential gear unit being adapted to be, in use, removably connectable to a shaft of a bag loader whereby two carrier tapes can be wound up on said spools with equal tension. 
   Thus the bag loader is less complex with only a single driving shaft and the high number of gears in the differential drive unit of the bag loader are no longer required. The gears of the differential gear unit of the apparatus of the present invention are only required to be used for one bag train and thus may be made of cheap materials, for example of injection moulded plastics. If the apparatus is to be reusable, harder wearing materials may need to be used. Thus, the next set of bags can be easily attached without tools and with only one component to fit onto a single shaft of the bag loader. 
   The apparatus dimensions can be vastly reduced compared to the cassette dimensions when the two spools were positioned side by side within the cassette. This is only possible because of the coaxial positioning of the differential gear unit with the spools. This results in a lowering of the cost of the apparatus because of the elimination of the need for a cassette housing or reduction in the bulk of the housing with the coaxial arrangement and, as the dimensions are less, the thickness of the walls for a given rigidity and strength can be reduced. The increased cost of the apparatus due to the need to provide it with a differential drive unit is offset by the reduced amount of material needed for the apparatus. 
   The present invention also provides a method of loading a bag train on a bag loader, comprising: taking a bag train incorporating a succession of imbricated packaging bags on two supply tapes from which they are to be removed during the loading operation, the supply tapes having lead ends equipped with two tape-winding spools with a differential gear unit is positioned coaxially between the spools; connecting the differential gear unit to a shaft of said bag loader; and driving said spools to wind up said tapes on said spools with equal tension to bring each of the imbricated bags successively to a loading position where the bag is loaded and separated from the tapes. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described by way of example only with reference to the accompanying drawings in which: 
       FIG. 1  is a perspective view of a bag train with cassette being loaded on to a bag loader; 
       FIG. 2  is an exploded view of a cassette of the present invention; and 
       FIG. 3  is an exploded view of the apparatus for taking up a succession of imbricated packaging bags of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows schematically how the present invention is employed in use on a bag loader machine  100 . A bag train  50  comprises a plurality of packaging bags  51   a ,  51   b ,  51   c  arranged in an imbricated way on two parallel carrier tapes  52   a ,  52   b  (usually about ½ bag width apart). The bags  51   a ,  51   b ,  51   c  are attached to the tapes  52   a ,  52   b  by adhesive. The end of the tapes  52   a ,  52   b  are positioned in a cassette  10 . The cassette  10  is loaded by hand, without tools, on to a shaft  112  of the bag loader  100  so that the unit is adapted to be, in use, removably connectable to the shaft. The adaptation may be by way of a snap-on fitting, a butterfly nut, an over center buckle etc. Any way of attaching the unit by hand, without the use of tools, so that little time or skill is required can be used. Although a door to protect the cassette  10  is shown in the figure, in practice this may not be necessary. The shaft  112  is rotated by motor  110 . The shaft  112  engages with the cassette  10  and drives the internal workings of the cassette to take up the tapes  52   a ,  52   b . On taking up of the tapes  52   a ,  52   b  the succession of bags  51   a ,  51   b ,  51   c  are brought closer to the bag loader machine  100 . As the tapes are taken up successive bags  51   a ,  51   b ,  51   c  can be removed from the tapes  52   a ,  52   b  and filled. 
   During drawing of the bags  51   a ,  51   b ,  51   c  towards the bag loader  100 , it is necessary to keep the tension in the two tapes  52   a ,  52   b  equal so that the bag openings, usually directed in the direction of advancement, remain in the same orientation to the bag loader  100  (i.e. usually parallel to the bag loader) such that the bags may be removed from the tapes automatically. In the present invention this is done by use of the cassette  10  which ensures that the tapes  52   a ,  52   b , as they are drawn in towards the bag loader around rollers or stationary pins  54   a ,  54   b , are kept in equal tension. This is achieved by the internal workings of the cassette  10  which are illustrated in  FIG. 2 . 
   The way in which the cassette  10  takes up the carrier tapes  52   a ,  52   b  with equal tension will now be described with reference to  FIG. 2 . The cassette  10  comprises two carrier tape winding spools  12   a ,  12   b  upon which the tapes  52   a ,  52   b  of the bag train  50  are to be wound. The spools  12   a ,  12   b  are enclosed in a housing of the cassette  10  comprising first and second components  14   a ,  14   b  which can, for example, snap fit together. A slot  15  formed in the first housing component  14   a  allows entry of the tapes  52   a ,  52   b  into the housing and thereby onto spool  12   a  for one tape  52   a  and spool  12   b  for the other tape  52   b . Two slots may be provided, one for entry of each tape  52   a ,  52   b . If those slots are positioned as far apart as the tapes are apart when attached to the bags, no rollers or pins  54   a ,  54   b  are required. The tapes  52   a ,  52   b  are attached to the spools  12   a ,  12   b  in any convenient way, for example through a hole in the outer flange of the spool and held in place by a pin inserted in the hole from the outside. The tapes  52   a ,  52   b  are wound around the spools  12   a ,  12   b  in the same direction. 
   The spools  12   a ,  12   b  are positioned coaxially with one another inside of the housing. Each of the spools  12   a ,  12   b  is depicted as having a central cut out  13  though this is not necessarily the case. In fact, only one of the spools  12   a ,  12   b  will require a central cut out  13  so that the shaft  112  of the bag loader can access a differential gear unit  20  positioned between and coaxially with the spools  12   a ,  12   b . The shaft  112  passes through the housing  14   b  in a cut out  16 , through the central cut out  13  of spool  12   b  to mesh with a mating hole  22  in a core  21  of the differential gear unit  20 . Thus, the spools  12   a ,  12   b  and core  21  of the differential gear unit are coaxial with the shaft  112  of the bag loader when the cassette is loaded on the bag loader. 
   Mounted on the core  21  is at least one bevel pinion  24 . In the preferred embodiment there are four bevel pinions  24  positioned symmetrically around the outside of the core  21 . The bevel pinions  24  are mounted to the core such that they can freely rotate around an axis perpendicular to the longitudinal axis of mating hole  22 . 
   The differential gear unit  20  is held substantially coaxially with said spools  12   a ,  12   b  by being positioned in recesses in the surfaces of the spools facing each other so that the spools can be positioned close together, possibly even touching. The action of engaging the cassette with the shaft  112  may serve to axially align the spools  12   a ,  12   b  and the core  21  of the differential gear unit and to hold them together. Alternatively, the spools and differential gear unit may be designed to snap fit together (or otherwise held together) without the aid of the cassette  10  or shaft  112  so that the shaft  112  only engages with the differential gear unit  20 . 
   Each of the spools  12   a ,  12   b  is provided with an integrally moulded bevel gear  26  (in the recess) which, when the cassette  10  is assembled, faces the other of said spools  12   a ,  12   b  and meshes with the bevel pinions  24 . In this way, if equal tension is present in the tapes  52   a ,  52   b  and the shaft  112  of the bag loader rotates the core  21 , the two spools  12   a ,  12   b  will be rotated at the same rate as the bevel pinions  24  will not rotate around their axis of rotation but the whole core and spool assembly will rotate at the same rate around the longitudinal axis of the shaft  112 . However, if tension in one of the tapes  52   a ,  52   b  decreases, the spool  12   a ,  12   b  on which that tape is wound will rotate faster than the other spool. This happens because the bevel pinions  24  will begin to rotate until the tension in the tapes  52   a ,  52   b  wound around their respective spools  12   a ,  12   b  is equalised. In this way it is possible to maintain the bag train  50  in an orientation such that each successive imbricated bag  51   a ,  51   b ,  51   c  will arrive at the bag loader in the perfect orientation for removal from the tapes  52   a ,  52   b  as the tapes  52   a ,  52   b  are taken up by the spools  12   a ,  12   b  of the cassette  10 . 
   As will be apparent, the cassette housing is not required for the correct functioning of the invention as shown in  FIG. 3 . The spools and drive unit could be individually directly assembled onto the shaft  112  or could be assembled on to the shaft  112  as one and be snap fitted or otherwise fixed together for convenience. A lip and flange on the core  21  to engage through a central through hole of the spools would be a satisfactory way of seeing to this. 
   The cassette housing components  14   a ,  14   b , spools  12   a ,  12   b  and the parts of the differential gear unit may all be formed by injection moulding of plastics material. This is cheap and the thus produced components easily have the durability to last for the entire bag train which can comprise several hundred bags. 
   It is envisaged that the cassette will be stored, for example during shipping, with the leading part of each of the tapes connected to the respective spool so that the entire bag chain  50  may be loaded onto the loader easily without first having to connect the tapes  51   a ,  52   b  onto the spools  12   a ,  12   b.    
   The cassette  10  can be re-usable. In use, the machine operator would attach the next bag train to the spools of a spare cassette whilst the machine is still working using another bag train. Once that other bag train is finished, the operator can substitute the old cassette for the spare one and restart the machine. 
   The present invention has been described by way of example only and variations are possible. In particular, as described above, the cassette  10  is not necessary for the functioning of the invention as shown in  FIG. 3 . The construction of the housing of the cassette could be varied.