Patent Publication Number: US-2004045926-A1

Title: Tamper evident cap wtih wavy ring seal

Description:
FIELD OF THE INVENTION  
       [0001] This invention relates to tamper evident caps. More particularly it discloses an improved cap of the type having a detachable tamper evident band.  
       BACKGROUND TO THE INVENTION  
       [0002] One known type of tamper evident cap hits an annular band which is attached around the bottom by frangible links such as a series of narrow ribs. The band is adapted to push over a shoulder moulded around a container neck during initial sealing thereof but subsequently break away and stay with said container when it is opened for the first time. A band which is separated from the cap therefore provides readily visible evidence that the container has been previously opened. Tamper evident caps provide consumers with assurance that the products they choose off supermarket shelves have not been interfered with. Difficulties have been encountered with the fitting of existing caps however due to uncontrollable variations in the shoulder diameter on moulded containers. In order to work the plain locking ring edges of current tamper evident bands (illustrated for example as the straight line free edge of flap  34  in prior art Australian patent 591512) must have a diameter which is within about ±0.6 mm per side of the mean shoulder diameter. With moulded glass bottles however the uncontrollable variation from the mean shoulder diameter can be as much ±1 mm. This variation causes either problems with the initial fitting of bands over shoulders at the outer tolerance limit or, with those shoulders at the inner tolerance limit, the failure of band separation during subsequent removal of the cap. Consequently with some moulded bottles the bands break during initial fitting and with others the bands subsequently come off and on freely with the caps. In the latter case the problem is exacerbated with moulded glass bottles as the shoulder edges cannot be made sharp and are therefore difficult to grip. In either case however no reliable evidence of tampering is provided to the consumer.  
       SUMMARY OF THE INVENTION  
       [0003] It is therefore an object of this invention to ameliorate the aforementioned disadvantages and accordingly a tamper evident cap of the type having a detachable annular band is disclosed, said band being adapted to push fit over a shoulder on the neck of a container during initial sealing of said cap thereon and to subsequently break away and stay with said container on removal of the cap to provide evidence of said removal wherein a shoulder engaging edge of the band is contoured to form resiliently deformable undulations around the circumference of said band to engage over a range of shoulder diameters.  
       [0004] Preferably but not essentially said waves are spaced at about 10 degrees around the circumference of said band.  
       [0005] It is further preferred that said edge is adapted to invert into the cap during initial sealing of said cap on the container.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0006] The currently preferred embodiments of the invention will now be described with reference to the attached drawings in which:  
     [0007]FIG. 1 is a cross-sectional view of a tamper evident ring seal plain cap according to a first embodiment of this invention before fitting onto a container.  
     [0008]FIG. 2 is a view similar to FIG. 1 but with the edge inverted after fitting onto the container,  
     [0009]FIG. 3 is a cross-sectional view along the lines A-A of FIG. 1,  
     [0010]FIG. 4 shows a partial cross-sectional view of a child resistant eyedropper cap constructed according to a second embodiment of this invention, and  
     [0011]FIG. 5 is a cross-sectional view of child resistant wadded cap constructed according to a third embodiment of this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0012] Referring first to FIGS. 1, 2 and  3  the cap is provided with screw threads  1  around the inside of the skirt  2  to mate with corresponding threads  3  on a moulded medicine bottle  4 . There are also flexible concentric flanges  5  formed inside the top of the cap which engage the upper lip  6  of the bottle to provide a fluid-tight seal. In accordance with this invention there is an annular tamper evident band  7  around the base of the skirt  2 . The band is attached by means of frangible angled ribs  8  which extend between an upper band edge  9  as shown and the bottom  10  of said skirt. The opposite lower portion of the band as best shown in FIG. 1 is shaped into a locking ring  7 A of reduced thickness and is connected to the main band portion  7  along a plastic hinge line  11  interrupted by spaced apart slits  12 . In accordance with this invention the free edge  13  of this locking ring  7 A is shaped to form undulations or waves which extend around the circumference of said ring. Although the invention is not limited to any specific dimensions, with this particular embodiment which is intended to fit a mean shoulder diameter of say 25 mm the inside diameter of the, band may be 27 mm, the height of the undulations may be about 1.5 mm and said undulations may be spaced about 10 degrees apart around the circumference of the ring. The aforementioned slits  12  are also preferably positioned to correspond with the peaks  15  of the undulations as best shown in FIG. 3. Each slit preferably also subtends an angle of about 10 degrees.  
     [0013] The initial configuration of the cap as moulded with the ring  7 A extending downwardly is shown in FIG. 1. This ring subsequently flips upwardly about the hinge line  11  upon push fitting and screwing of the cap onto the threaded bottle neck  16  as shown in FIG. 2. The undulating edge  13  is thus directed upwardly so that the peaks  15  seat in a recess  17  formed under the shoulder  18 . The edge  13  thereby secures the locking ring onto the neck of the bottle so that subsequent removal of the cap breaks the angular ribs and separates the band to stay with the bottle and provide evidence of the opening  
     [0014] The forces exerted by the ring  7 A on the band  7  during the aforementioned assembly process are resisted by support pods  18 A formed around the upper edge  9  of Said band. In particular the shear forces between the skirt  2  and the band  7  are resisted by drive dogs  18 B reacting against these pads  18 A so that the angled ribs  8  do not separate.  
     [0015] It has been found by the inventor that by virtue of the wavy or undulating shape described above the locking ring works over a wide range of dimensional variation which on the aforementioned mean shoulder diameter may be ±5 mm. This range is much greater than prior art plain edged rings can function with. Even with those bottles having the smallest allowable shoulder diameter the inner peaks  15  of the inverted ring  7 A after passing over said shoulder spring back sufficiently to secure the band against removal. With those shoulders having the largest allowable diameter at the other end of the tolerance range the peaks  15  resiliently compress enough for the band to fit without premature fracture. In this latter case the slits  12  have been found to assist the compression of the ring.  
     [0016] With the second and third embodiments of FIGS. 4 and 5 a locking ring according to this invention is shown fitted to child resistant caps. The main components of these caps which correspond in function to those of FIGS.  1  to  3  are indicated by the same numbers which however are primed (″) and (′″) to distinguish them. These caps have threaded skirts fitted within cowlings indicated respectively as  19 ,  20  and  21 ,  22 . The cowlings  20 ,  22  are movable relative to said skirts between first positions at which the cowlings engage lugs  23 ,  24  on the skirts when turned in a rotational direction to screw the skirts onto a container such as a bottle and a second position at which the skirts are engaged by the cowlings in the opposite rotational direction to enable the skirts to be unscrewed. There are also cam surfaces  25 ,  26  on the cowlings which engage inclined shoulders  27 ,  28  on the skirts to biase the cowlings to the first position. The second embodiment of FIG. 4 also has an eyedropper  29  fitted.  
     [0017] It will thus be appreciated that this invention at least in the form of the embodiments disclosed provide a novel and useful improvement in the construction of tamper evident caps. Initial trials have shown that one size of tamper evident band constructed according to this invention can work over a much wider range of shoulder diameter variations than prior art bands. This reduces manufacturing costs and produces a better performing product. Clearly however the examples described are only the currently preferred forms of the invention and a wide variety of modifications may be made which would be apparent to a person skilled in the art. For example the design of the tamper evident band as well as the number, shape and configuration of the undulations in the locking ring may be changed following further development by the inventor. Also, while it is currently preferred to mould the cap from polypropylene other suitable materials may be used.  
     [0018] Expressions such as “upper”, “lower”, “bottom” and “downwardly” etc. refer to the caps in one position of use as illustrated and are not to be read as necessarily limiting.