Patent Publication Number: US-7904995-B2

Title: Bi-material closure device for a bag

Description:
This present invention concerns the area of closure zippers designed to perform multiple opening and closing of bags. 
       FIGS. 1 and 2  show an example of known closure zippers. 
     These two figures respectively show two closure assemblies  10  each with two complementary zippers  20 ,  30 . 
     More precisely these two assemblies  10  each have two zippers  20 ,  30  that include support backing-strips  22 ,  32  which carry complementary closure elements  24 ,  34 . According to  FIG. 1 , these elements  24 ,  34  are formed from complementary male/female structures. According to  FIG. 2 , these elements  24 ,  34  are formed from complementary hooks. 
     Many closure zippers of the type shown in  FIGS. 1 and 2  have already been proposed. 
     Generally, these closure zippers are extrusions made from thermoplastic materials. 
     However it is proving desirable now, for certain applications, to have bi-material closure zippers, meaning zippers in which the backing-strips  20 ,  30  and the closure elements  24 ,  34  are made from different materials. In theory, this should enable one to create closure assemblies that have, for example, different colours or even different degrees of flexibility between the backing-strips  20 ,  30  and the associated closure elements  24 ,  34 . To this end, an attempt has been made to co-extrude backing-strips  20 ,  30  and closure elements  24 ,  34  made from different materials, as shown diagrammatically in  FIG. 3  attached, for closure elements  24 ,  34  of the male/female type. 
     Up to now however, these attempts have not given total satisfaction. In fact, they present a persistent risk of separation of the closure elements  24 ,  34  in relation to the support backing-strips  20 ,  30  when the bags pulled open, or again under the simple effect of pressure inside the bag. 
     In this context, this present invention has as its objective to perfect the existing resources. 
     This objective is attained in the context of this present invention by virtue of a closure assembly that includes two complementary zippers respectively with support backing-strips and complementary closure elements, characterised by the fact that at least one of these closure elements includes a widened soleplate which is at least partially surrounded by the associated support backing-strip. 
     The professional engineer will understand that this arrangement enables the closure element to be retained on the support backing-strip, thereby eliminating any risk of separation between the closure element and the associated support backing-strip. 
    
    
     
       Other characteristics, objectives and advantages of this present invention will appear on reading the detailed description that follows, with reference to the appended drawings, provided by way of non-limiting examples and in which: 
         FIGS. 1 to 3 , described previously, represent closure assemblies according to existing designs, 
         FIG. 4  is a view in cross-section of a closure zipper according to this present invention, and 
         FIGS. 5 to 12  represent diverse variants for the creation of closure zippers according to this present invention. 
     
    
    
       FIG. 4  shows a closure zipper according to this present invention that includes a closure element  240  of the female type that has a channel  242  with converging edges connected to a rod  244  which is generally perpendicular to the main surfaces of a support backing-strip  220 . According to the invention, the rod  244  is equipped, at the end opposite to the channel  242  with converging edges, with a widened soleplate  246  embedded in the mass of the backing-strip  220 . In other words the soleplate  246  is totally surrounded by the material of the backing-strip  220 . It is located in a cavity formed in the thickness of the backing-strip  220 . 
     Preferably, the backing-strip  220  and the associated closure element  240  shown in  FIG. 4  are co-extruded in thermoplastic materials. 
     The technique of co-extrusion is well known to the professional engineer. It will therefore not be described in detail in what follows. 
       FIGS. 5 and 6  show two variants for the creation of closure zippers according to this present invention, which differ from the zipper shown in  FIG. 4  only by the fact that the closure element  240  is composed of an element  242  of the male type in  FIG. 5  and an element of the hook type in  FIG. 6 . 
     The soleplate  246  lies symmetrically on either side of the rod  244  according to the variants shown in  FIGS. 4 to 6 . 
     On the other hand, according to the variant shown in  FIG. 7 , the soleplate  246  is asymmetrical in relation to the rod  244 . More precisely, according to  FIG. 7 , it lies only on one side of the rod  244 . According to yet another variant, not shown in the figures so as to simplify the illustration, the soleplate  246  could lie on either side of the rod  244 , but along different extensions. 
       FIG. 8  shows another implementation variant according to which the support backing-strip  220  has a variable thickness at the location of the soleplate  246 . More precisely, again according to the implementation variant shown in  FIG. 8 , the backing-strip  220  has an increasing thickness close to the rod  244 . This arrangement is used to strengthen the retention of the closure element  240  on the support backing-strip  220 . 
     As shown in  FIG. 9 , where appropriate, structures of complementary shape can be provided, interleaved between the backing-strip  220  and the soleplate  246  in order to reinforce the retention of the closure element  240 . More precisely, again according to the method of implementation shown in  FIG. 9 , at least one low ridge  222  is provided, cast in the material of the support backing-strip  220  and engaged in a complementary channel  247  formed in the soleplate  246 . According to  FIG. 9 , two such low parallel ridges  222  are provided, respectively adjacent to the rod  244  on either side of the latter. 
     According to the implementation variant shown in  FIG. 10  the soleplate  246  is accessible on the face  224  of the support backing-strip  220  opposite to the face  225  of this support backing-strip by which the rod  244  bearing the closure element  242  emerges. 
       FIG. 11  shows a variant according to which the soleplate  246  emerges on the face  224  of the support backing-strip opposite to the closure element  242 . However, according to the variant shown in  FIG. 11 , at the level of this face  224  of the support backing-strip  220 , the soleplate  246  is partially covered by ribs  226  cast in the material of the support backing-strip  220 . This arrangement is used to eliminate the risk of extraction of the soleplate  246  via the face  224  of the support backing-strip  220 . 
     For the hook-type closure elements,  FIG. 12  shows that this present invention can apply to support backing-strips  220  that have several closure elements in parallel. 
     It will be seen that the characteristics of this present invention, according to which at least one of the closure elements includes a soleplate that is at least partially embedded in a support backing-strip, applies either to the creation of closure assemblies as such that are intended to be assembled later and secured onto a film, by welding for example, or to closure assemblies that are directly integrated by extrusion in films that are intended for the design of bags. 
     This present invention applies in particular to closure assemblies in which the support backing-strips  220  and closure elements  240  are made from different thermoplastic materials. This arrangement is used, for example, to create a support backing-strip  220  and an associated closure assembly  240  in different colours or with different degrees of flexibility. 
     In this context, the materials making up the support backing-strip  220  and the closure element  240  are advantageously chosen from the group that includes polyethylene, polypropylene and polystyrene. 
     More precisely and again preferably, according to the invention, the support backing-strip and the associated closure element  240  matching the configurations described previously are preferably chosen from the pairs that include polyethylene and polypropylene or polyethylene and polystyrene. 
     The implementation variants shown in  FIGS. 7 to 11  are illustrated with a closure element  242  of the female type. However the invention is not limited to this arrangement. All the characteristics shown in  FIGS. 7 to 11 , as well as those illustrated in  FIG. 12 , are liable of be applied to any type of closure element  242  whether of the female, male or hook type or any other equivalent shape. 
     In addition, the invention also covers any combination of the characteristics described previously and shown in the appended figures.