Tamper-Indicating Closure

The utilization of tamper-indicating closures, in which the closure is of a thermoplastic material, is receiving wide acceptability in the marketplace. Such closures will become even more market dominant upon their acceptance by the carbonated beverage industry. Exemplary of various types of tamper-indicating closures are the ones shown in U.S. Pat. Nos. 3,329,295, 3,438,528, 3,784,041, 4,126,240, 4,147,268, 4,196,818, 4,206,851, and 4,305,516.

It is an object of this invention to provide a tamper-indicating closure which features high fidelity in operation and simplicity in construction and manufacture.

This invention relates to an integrally-formed tamper-indicating thermoplastic closure for fitment to a container having a threaded neck portion and an outwardly extending annular flange adjacent to and beneath the threaded neck portion. The thermoplastic closure of this invention can be produced by conventional injection-molding techniques. A particularly useful thermoplastic material, from which the closures of this invention can be made, is polypropylene. However, other thermoplastic materials may be useful such as polyethylene terephthalate, high-density polyethylene, nylon, polyvinyl chloride, etc.

The closure of this invention features a conventional top wall and an annular sidewall downwardly depending therefrom. About the inside surface of the annular sidewall, there is provided a closure thread for cooperation with the container thread to achieve fitment of the closure to the container. Connected to the lower end of the annular sidewall, by way of an annular frangible area, is an annular tamper-indicating band. The annular tamper-indicating band is dimensioned, along with the annular frangible area and the annular sidewall, so that the band will at least partially extend to a point beneath the container's outwardly extending annular flange when the closure is fitted to the container. The annular frangible area can be of any configuration which allows for fracturing in this area upon attempted removal of the closure from the container. Fracture of the annular frangible area results in separation of the annular tamper-indicating band from the closure's annular sidewall. The annular frangible area can be defined by a plurality of spaced-apart fracturable bridges. Such bridges will lack sufficient strength to maintain their integrity upon attempted removal of the closure from the container. Also, the annular frangible area can be defined by a continuous groove which defines an annular area of reduced thickness. Generally speaking, if the closure is made of polypropylene, this annular area would have a thickness within the range from about 0.003 to about 0.008 inches.

The annular tamper-indicating band features an annular upper portion which depends downwardly from the annular frangible area. The band additionally has an annular lower portion which comprises a plurality of spaced-apart tabs with each tab connected to its neighboring tab by way of a flexible web. Each of the tabs has an outwardly extending projection at its lower extent. These projections will, when the tabs are turned inwardly and upwardly, each provide a surface which will be placed in a position of interference with the container annular flange when the closure is fitted to the container. To connect the annular upper portion to the annular lower portion there is provided an annular hinge. The annular hinge can be provided by a continuous thinned wall web or it can be provided by a plurality of thinned wall hinges which are separated one from the other by slots or openings. In this latter configuration, each of the thinned wall hinges will be connected to adjacent corners of neighboring tabs.

These and other features of this invention contributing to satisfaction in use and economy in manufacture will be more fully understood when taken in connection with the following description of a preferred embodiment of this invention and the accompanying drawings in which identical numbers refer to identical parts and in which:

FIG. 1 is a sectional view of a closure of this invention fitted to a container;

FIG. 2 is a sectional view of the closure shown in FIG. 1 as the closure is removed from the container;

FIG. 3 is a partial enlarged sectional view of the closure shown in FIG. 1 with the tamper-indicating band at its midway point as it is turned inwardly;

FIG. 4 is a partial enlarged sectional view of the closure shown in FIG. 1 showing the position of the tamper-indicating band after it has been hinged inwardly;

FIG. 5 is a perspective view of the closure shown in FIG. 1;

FIG. 6 is a sectional view taken through sectional line 6--6 in FIG. 5;

FIG. 7 is a bottom plan view of the closure shown in FIG. 1;

Referring now to FIGS. 1-7, there can be seen a package, generally designated by the numeral 10, composed of a closure of this invention, generally designated by the numeral 12, and a container, generally designated by the numeral 14.

Container 14 can be of any conventional material, for example, it may be of a thermoplastic material such as polyvinyl chloride, polyethylene terephthalate, polyethylene, etc., or it may be of glass. Container 14 has a neck portion which carries on its outside wall a helical thread 16. Beneath, but adjacent to helical thread 16, is annular outwardly extending flange 18. Note that annular flange 18 has an upper annular surface which is sloped downwardly to meet an essentially horizontal lower annular surface. Such a configuration is advantageous when utilizing closures of this invention as hereinafter described.

Closure 12 has a circular top wall 20 and an annular downwardly depending sidewall 22. About the inside surface of annular sidewall 22 is a helical closure thread 24. Closure thread 24 is configured and dimensioned to be cooperative with container thread 16 to achieve fitment of cap 12 onto container 14. Nested against the inside surface of top wall 20 is liner 21. Liner 21 is utilized to effect a seal between closure 12 and the mouth of container 14 as is seen in FIG. 1. However, it should be realized that the closures of this invention are not limited to the utilization of a liner to effect this sealing but that the closures of this invention can also utilize linerless sealing systems which are well-known to those skilled in the art. Generally speaking, such linerless systems utilize downwardly extending fins which emanate from the inside surface of top wall 20, or at the juncture of top wall 20 and annular sidewall 22. These fins coact with the mouth portion of container 14 to achieve the desired seal.

Closure 12 has integrally formed with sidewall 22, annular tamper-indicating band 26. Annular tamper-indicating band 26 is attached to sidewall 22 by way of annular frangible area 28. Annular frangible area 28 is an area of reduced strength which is designed to fracture in accordance with the tamper-indicating operation of closure 12. For the embodiment shown in the drawings, annular frangible area 28 is formed by a plurality of slots 32 which alternate with a plurality of fracturable bridges 30. The width and depth of fracturable bridges 30 will be dependent upon the expected stresses to be applied thereto on closure opening and upon the material which closure 12 is made. For example, if the closure is made of polypropylene, and there are 8 to 12 fracturable bridges equiangularly spaced about annular frangible area 28, then for conventional usage, fracturable bridges 30 can be designed to have a width of from about 0.020 to about 0.030 inches and a depth of from about 0.0070 to about 0.010 inches. In any event, the configuration ard dimensions of fracturable bridges 30 is best determined by empirically testing the closure on a container and under the conditions expected to be encountered in the marketplace.

Annular frangible area 28 may also have other configurations. For example, this area may be formed by a groove cut into the outside of the closure sidewall. The groove defines an annular area of reduced thickness and thus would represent a zone of weakness capable of shearing upon removal of closure 12 from container 14. Other frangible area configurations may be used since the particular configuration is not critical to the operation of the closures of this invention so long as the frangible area is capable of shearing or fracturing under conventionally expected removal forces.

Immediately below annular frangible area 28 is annular tamper-indicating band 26. Annular tamper-indicating band 26 has an annular upper portion 34 attached to annular lower portion 38 by way of annular hinge 36. Annular hinge 36 is an annular area of reduced thickness which allows for flexing along the annular line defined by annular hinge 36. The thickness of annular hinge 36 is dependent upon the material from which closure 12 is made. Some thermoplastic materials will exhibit greater resistance to bending and thus need to be made fairly thin. Other thermoplastic materials, however, are easier to bend but need a greater thickness to guard against stress fracture. It has been found that when utilizing polypropylene as the material of construction for closure 12, that annular hinge 36 should have a thickness within the range of from about 0.0080 to about 0.014 inches.

Annular lower portion 38 is comprised of a plurality of spaced apart tabs 40 which are connected by way of flexible webs 42. At the lower portion of each tab 40 there will be a projection 44. For the embodiment shown the projections are triangular. Triangular projections 44 each will present a substantially horizontal surface to the essentially horizontal lower annular surface of annular flange 18 so that a position of interference will be effected when closure 12 is fitted to container 14. Other configurations for the projections may be used so long as the position of interference is achieved between the projection and the annular flange and so that this position of interference is stout enough to be maintained when the closure is removed from the container. Not only do the projections serve to provide the just described interference, but they also serve to rigidify tabs 40. Rigidification of tabs 40 may be desirable to maintain the position of interference when the closure is of a thermoplastic material which is too flexible without the projections to maintain the interference position during closure removal.

Functionally, the closures of this invention are the paragon of simplicity. As is shown in FIG. 5, closure 12 is molded so that annular tamper-indicating band 26 is in the down position. To prepare closure 12 for use on container 14, it is necessary to fold inwardly and upwardly lower portion 38. The folding will occur about annular hinge 36. This inward and upward fold requires that annular lower portion 38 have the circumferential flexibility to accommodate the varying circumferences encountered as it moves from its molded position, shown in FIG. 5, through the intermediate position shown in FIG. 3 and the final at rest position shown in FIG. 4. As can be seen in FIG. 3, the inward folding of annular lower portion 38 results in its having a reduced circumference at its end most distal from annular hinge 36. This reduction in circumference and the resultant stress, however, is at least partially accommodated by the folding of flexible webs 42. Once annular lower portion 38 passes through the position shown in FIG. 3 towards the position shown in FIG. 4, the stresses realized are abated. When annular lower portion 38 is in the FIG. 4 position, the various forces acting on it are in equilibrium. As can be appreciated, annular hinge 36, since it is of a resilient material, will be urging return of annular lower portion 38 to its original molded position, shown in FIG. 5. However, to arrive at this position, it will be necessary to apply sufficient force to pass annular lower portion 38 back through the position of FIG. 3. As mentioned previously, the position of FIG. 3 is a stress position and thus, considerable force must be utilized to go through that position. The resiliency in annular hinge 36 is not sufficient to effect such movement of annular lower portion 38. Annular lower portion 38 therefore is held in the position shown in FIGS. 1, 2 and 4. Note also that annular lower portion 38 is positioned slightly outwardly from the inside surface of sidewall 22. This position can be encouraged by the placing of annular hinge 36 outside of the inside wall of annular upper portion 34 so that the lower inside part of annular upper portion 34 abuts against tabs 40 as shown in FIG. 4 at "Y". This positioning of annular lower portion 38 inwardly of the inside surface of the closure sidewall is advantageous in that it ensures that tabs 40 of annular lower portion 38 make good interfering contact with annular container flange 18. This interfering contact can be achieved without displacement of annular lower portion 38 from the inside surface of sidewall 22 by providing projections on the tab and/or on the lower inside part of annular upper portion 34. These projections will provide the interfering contact which is desired.

The inward and upward folding of annular lower portion 38 is accomplished after the injection molding of closure 12. This inward folding can be accomplished by utilization of simple punching means as is well known to those skilled in the art.

Once annular lower portion 38 has been folded inwardly to the position shown in FIGS. 1 and 4, the closure can be simply screwed onto container 14. As closure 12 is screwed onto container 14, annular lower portion 38 will make contact with annular container flange 18. Since annular container flange 18 has a downwardly sloped upper annular surface to act as a cam surface and annular lower portion 38 is resiliently hinged, passage of annular lower portion 38 thereover is facilitated without the realization of great stress in annular frangible area 28. By having annular lower portion 38 resiliently hinged, a spring action is realized as annular lower portion 38 passes over annular container flange 18. Therefore, annular lower portion 38 is able to flex resiliently away from container annular flange 18 thereby mitigating stress caused by the passage of annular lower portion 38 over annular container flange 18.

After closure 12 has been fitted to container 14, it can be seen that the bottom surfaces (now the top surfaces) of triangular projections 44 are in abutment against the horizontal lower annular surface of annular flange 18. This position assures an interfering fit between the horizontal lower annular surface and triangular projections 44 which can only be overcome by forces which are larger than can be withstood by annular frangible area 28. Further, since the forces of removal bear on annular lower portion 38 through its vertical width it is placed in compression and since annular lower portion 38 is strongest against deformation due to compression the rigidity of the interfering fit is enhanced during closure removal.

As unthreading of closure 12 occurs, closure 12 will move axially and upward in response to the unthreading torque. Annular tamper-indicating band 26, however, is blocked from such axial upward movement due to the before-mentioned interference between triangular projections 44 and the horizontal lower annular surface of annular flange 18. Continued application of torque onto closure 12 will result in tension forces being realized throughout the entire closure sidewall area. Since annular frangible area 28 is the weakest link throughout the closure sidewall area, a fracture will ultimately occur there (see FIG. 2). After fracture the tamper-indicating system of closure 12 provides that annular tamper-indicating band 26 will remain with the container. Closure 12 is free to be removed from the container for dispensing of the products contained therein. The fact that annular tamper-indicating band 26 is separated from the rest of the closure is a sign of prior entry into the container.