GB2062593A

GB2062593A - Tamperproof closure

Info

Publication number: GB2062593A
Application number: GB8033069A
Authority: GB
Original assignee: Ethyl Products Co
Current assignee: Ethyl Products Co
Priority date: 1979-10-22
Filing date: 1980-10-14
Publication date: 1981-05-28
Also published as: JPS5695855A; ES263098U; JPS624305B2; FR2467790A2; GB2062593B; FR2467790B2; ES263098Y; DE3039502A1; DE3039502C2

Abstract

A thermoplastics material tamperproof closure, e.g. a screw closure, comprises a top wall 12, a side wall 14 and, attached to the side wall by a plurality of spaced apart ribs 16 a band, the band and ribs being heat-shrinkable and the band being so-structured that is acquires at least one region 20 of reduced cross- sectional area after the application of heat thereto as it shrinks to adopt (after the closure is fitted to the container) a position where removal of the closure from the container will fracture the band, Fig. 6 (not shown), e.g. the band may be shrunk to a position of interference under the container flange 34 when such flange is present. A method of injection moulding the closure to produce the required band structure is described. <IMAGE>

Description

SPECIFICATION Tamperproof closure This invention relates to so-called tamperproof closures.

The utilization of tamperproof closures is well known in the art. A particularly ubiquitous tamperproof package features a closure fittable to a container having a neck and an outwardly extending flange beneath the neck. The closure has a non-fracturable band attached to the closure at the lower end of the closure skirt by a plurality of fracturable ribs. This style closure is generally fitted to the container so that the band will achieve a position of interference under the container flange. Removing the closure from the container results in axial movement of the main closure body which movement cannot be followed by the non-fracturable band as it is in interference with the container flange. As more axial force is applied to the closure, the fracturable ribs fracture allowing the closure to separate from the band and be removed from the container.An example of such a tamperproof package is shown in U.S.

Patent Specification No. 3,438,528.

Another style of tamperproof package is the one disclosed in British Patent Specification No. 1495230. A closure, in this style package, utilizes a band which is separated from the main closure body upon fitment of the closure to the container. Final fitment of the closure to the container results in a plurality of tongues engaging the separated band so that when the closure is removed from the container body the separated band is fractured thereby giving an indication that the package has been tampered with.

While the above systems have merit, they have one serious drawback; i.e. a ring or band of plastics material remains with the container after the main portion of the closure has been removed from the container. This often results in the user of these style packages dropping the separated band into the product as it is dispensed into a cup or glass. The user of the package must then attempt to locate and remove the band from the dispensed product, resulting in aggravation and possible contamination of the product. In those instances where the user does not note the falling of the band into his cup or glass there is a very real danger that injestion of the band will occur with all of its attenuant medical difficulties.

It is an object of this invention to provide a closure that retains, as a unitary piece, its tamperindicating parts. Such a closure may be designed for use either with or without a sealing liner.

According to the invention there is provided a thermoplastics material closure forfitment to a container having a neck with a means for removably attaching the closure to the container, which closure comprises a top wall, a side wall and an annular band attached to the sidewall by a plurality of spaced apart ribs, the band and ribs being heat-shrinkable upon the application of heat thereto and the band being so-structured that, upon said application of heat, after the closure has been fitted to the container, at least one region of reduced cross-sectional area is produced in the band as the band is shrunk around the container neck.

It is preferred that the closure be adapted for fitment to a container having an outwardly extending flange beneath means on the neck for removably attaching the closure to the container, the closure ribs being of sufficient length so that the band is below the flange when the closure is fitted to the container.

Usually, the band is substantially uniform in cross-sectional area and has a plurality to regions of reduced strength, the positions of such regions alternating with the positions of the ribs and said regions having a reduced cross-sectional area after said application of heat after the closure has been fitted to the container.

Preferably the attaching structure for the closure and container comprises cooperating helical threads. To provide a leak-proof seal, the closure of this invention can have either a sealing liner seated against the inside surface of the top wall or an annular sealing fin downwardly depending from the top wall and adapted to form a liquid-tight seal with the uppermost extent of the container neck.

Preferably the closure of this invention is made of a thermoplastics material selected from polypropylene, polyethylene terephthalate or high density polyethylene.

In our copending Application No. 8006074, a closure is described which has an annular band attached by a plurality of ribs to a closure sidewall with the band having at least one fracturable area.

As seen in the drawings of the application, which disclose a preferred embodiment, the band has a plurality of molded areas which are of a crosssectional area less than the remainder of the band and which constitute the fracturable areas. In contrast, the closure of the present invention has, in use, areas of reduced cross-sectional area which, instead of being molded in ab initio, are formed upon application of heat to the annular band and its consequent shrinkage after the closure is fitted to the container. This phenomena, i.e. reduction in cross-sectional area upon the application of heat to the fracturable areas, is believed to be directly related to the method by which the closures of this invention are produced; however, the scope of this invention is not limited to this theory.

Formation of a closure in accordance with this invention may be achieved by the utilization of injection molding techniques in which a molten thermoplastics material is injected into a mold formed by male and female mold portions. The plastics material is injected so that it enters the mold, preferably near the centre of the top wall mold cavity so that it radiates in a direction to form the top of the closure and then down to form the sidewalls. As the sidewalls are filled, the molten plastics material moves to the rib cavities and into the cavity defining the annular band.

Since the material enters the band cavity only from the various rib cavities, the thermoplastics material will move circumferentially along the band cavity only from the various rib cavities, the thermoplastics material will move circumferentially along the band cavity from each of the ribs so that thermoplastics material from one rib cavity will meet thermoplastics material from the adjacent rib cavity at a point therebetween. This meeting point of the material forms a unique condition at the point of intersection which, for convenience, will be called a weld line or knit line. This weld line or knit line will ultimately form a fracturable area. Although the weld lines (there is usually one between each pair of ribs) are nearly invisible to the naked eye, they have structural properties different from the adjacent material which make up the rest of the annular band.It is believed, even though the scope of this invention is not restricted to this theory, that the knit lines have a dual molecular structure.

The centre of the knit line is believed to have a molecular structure which is interlocked as the thermoplastics material emanating from one rib makes molten contact with thermoplastics material emanating from the adjacent rib. As one views the weld line or knit line and moves towards the outer edges thereof, it is found that molecular structure is not interlocked due to the failure of molten thermoplastics material meeting molten thermoplastics material as is the case for the centre portion of the weld or knit line. This failure to have molten material to molten material contact is due to the edges of the material being in contact with the cooler metal mold which partially solidifies the outer surface of the material while the interior of the moving thermoplastics material remains molten.The cooler skin has a greater friction against the mold surface than the interior molten material and thus has a reduced velocity.

As a result, the cavity fills due to the inside molten theremoplastics material continually pushing ahead and breaking through the colder frontal skin. At the point where the two separate flows come together the cold frontal skins of each flow make contact and are forced together by the interior mass still under injection molding pressure. At this point only a small amount of molten material from the interior of each flow can break through and form a homogeneous mass and thus interconnection. The result is a tubular sandwich structure with the outer walls touching end to end but where the molecular structure is not interlocked and where the interior of the sandwich is molecularly interlocked due to the mixing of the inside molten material.

Thus, the invention includes a process for forming a closure of the invention by injection molding which comprises injecting molten thermoplastics material into a mold, the interior of which corresponds in shape to the desired closure, so that plastics material fills the top wall-shaped cavity and moves down to fill the sidewall-shaped cavity, the rib-shaped cavities and finally the band-shaped cavity, allowing the plastics material to set and removing the resulting closure from the mold.

To the naked eye the band will usually have a uniform cross-section until application of heat to the band. Upon application of heat by a stream of hot air, for example, the thermoplastics material band begins to shrink around the container neck, drawing itself under the container flange in preferred embodiments. At the knit of weld lines the portions of the lines which are not molecularly interlocked will pull away from each other. At the centre of the knit or weld line where there is molecular interlocking the band will actually have to stretch a bit to follow the rest of the shrinking band. This stretching in combination with the above-described characteristics of the knit or weld lines results in fracturable areas having a crosssectional area less than the cross-sectional area of the rest of the band.After shrinkage of the band, application of axial force on the closure to remove it from the container will result in the shrunken band rupturing at these areas of reduced crosssection. Thus, when the container has a flange, the band has to pass over the flange and rupturing will result since the diameter of the shrunken band is less than the outside diameter of the flange. Since, upon fracture, the aforesaid areas are highly visible, the tamperproof function is achisved.

In the process of applying heat to the annular band and ribs, control of exposure time and temperature must be calibrated to achieve the desired results. In general, the higher the temperature the shorter the time and vice versa.

For example, on a high speed filling line where bottles are normally filled and capped at rates of 240-600 bottles per minute on a continuous motion basis, the time available to heat shrink each rib and band set is very limited. Consequently high temperatures, i.e. temperatures which are capable of shrinking the thermoplastics material, are used, but the exposure time is carefully controlled to produce the desired degree of shrinkage in the band without damaging the rest of the closure. The desired degree of shrinkage is defined as that which: (1) causes the tamperproof band to pull in around the container neck, e.g.

under the container flange (when a flange is present) to a smaller diameter than that of the outside diameter of the flange; (2) causes the aforementioned reduction in the cross-sectional area of the fracturable parts, i.e. the weld lines or knit lines, but not such a reduction as to cause fracture of the areas due to the heating; and (3) causes the fracturable areas to stretch beyond the thermoplastics material's elastic limit whereby fracture will occur only during the removal of the closure.

One practical method to achieve the range of conditions satisfying the above criteria on a commercial bottle filling line consists of a narrow slit forced air duct directing a horizontal stream of hot air at the annular band. The bottles are mechanically caused to rotate as they pass through the hot air stream. The air temperature is controlled by a variable transformer if the heat source is electrical, or by suitable valves if gas or other fuel is used. Secondly, the velocity of the hot air stream is controlled by suitable valving. The speed of the conveyor upon which the bottles are riding is adjusted to provide suitable exposure time for the annular band. Adjustment of the temperature and time of exposure utilizing a system such as the one described above is well within the skill of those knowledgeable in the art.

Other methods may be utilized to apply heat to the annular band and will be found to be equally valuable as long as the criteria mentioned previously are adhered to.

The present invention naturally includes a combination of a closure of the invention and a container to which the closure is fitted.

Preferably, in such a combination, the container comprises a body portion, a neck portion having means for removably attaching the closure and an outwardly extending flange beneath said attaching means on the neck, the closure being of sufficient length so that the closure band is below the flange and the band and ribs having been shrunk by the application of heat thereto so that the band nests in a position of interference under the flange.

The container may, for example, be made from polypropylene or polyethylene terephetalate or glass.

The invention will now be further described and illustrated by reference to the accompanying drawings, in which identical numerals refer to identical parts, and in which: Figure 1 is a top plan view of a closure in accordance with this invention; Figure 2 is a side elevational view of the closure shown in Figure 1; Figure 3 is a bottom plan view of the closure shown in Figure 1; Figure 4 is a partial sectional view of a tamperproof package of this invention showing the application of heat to the closure to shrink the annular band; Figure 5 is a side elevational view of the package shown in Figure 4 with the annular band secured under the container flange; Figure 6 is a side elevational view of the package shown in Figure 4 with the closure being moved from the container and the resultant fracturing of the annular band; and Figure 7 is a partial sectional view of the tamperproof package of this invention utilizing a closure as shown in Figure 1 but with a sealing fin being provided.

Referring now to Figures 1-6, it can be seen that a closure in accordance with this invention, generally designated by the numeral 10, is fittable to a container, generally designated by the numeral 30 in Figures 4-6. Closure 10 has a top wall and an annular downwardly depending sidewall 14. Sidewall 14, for the embodiment shown, has a serrated outside surface. By having such a surface, the user of the closure of this invention is given a better grip for applying the necessary torque to remove and replace the closure 10 on container 30. It is understood that a smooth outside surface, or for that matter, any other outside surface treatment is without the scope of this invention, the exact configuarion of the outside surface being ieft up to the manufacturer of closure 10.In Figure 4 there is shown helical closure thread 24 which is about the inside surface of sidewall 14. Closure thread 24 cooperates with container thread 38 to tighten closure 10 onto container 30. Other means for achieving container-closure attachment may be used, e.g. bayonet lock, cam action or snap-on finish.

Seated against the inside surface of top wall 12 is sealing liner 22. Sealing liner 22 can be any of the multitude of liners commercially available which will effect a liquid-tight seal for the package shown in the drawings. Downwardly depending from the lowermost end of sidewall 14 is a plurality of non-fracturable ribs 1 6. These ribs have attached at their other ends band 1 8 which has a plurality of fracturable portions or areas 20 of reduced strength. Note that in Figures 2 and 3 fracturable areas 20 have a cross-sectional area essentially equal to the cross-sectional area of the rest of band 1 8.

Ribs 1 6 are non-fracturable and therefore are dimensioned to withstand the stresses placed upon them prior to the fracture of fracturable areas 20. Due to the method of manufacture, fracturable portions 20 will alternate along band 1 8 with the points of connection of band 1 8 with ribs 1 6. Thus there will be the same number of portions 20 as there are ribs 1 6.

Another embodiment is shown in Figure 7 and is nearly identical to the embodiment shown in Figures 1-6, identical numbers identifying identical parts. The one difference is that the closure shown in Figure 7 does not utilize a sealing liner but, rather, utilizes a sealing fin 35.

Sealing fin 35 is annular in shape and is dimensioned so that it will bear upon the uppermost extent of the container neck. As mentioned previously, the exact configuration of sealing fin 35 can be of any convenient design, the package of this invention not being limited to the sealing fin design shown in Figure 7. For example, sealing fin 35, instead of being a single fin, may be bifurcated fin. Fin 35 may also be designed to form a liquid-tight seal with the inside surface of the container neck rather than seating upon the top of the container neck as shown in Figure 7.

Many variations of sealerless liners known to those skilled in the art may be utilized as long as they do not interfere with the tamperproof qualities of the package of this invention.

Container 30, as before mentioned, may be of glass or any suitable thermoplastic material.

Container 30 can be conventionally provided with flange 32 which will be utilized as a convenient way of holding container 30 on the fill line.

Beneath container thread 38 there is provided an annular outwardly extending flange 34. Outward flange 34 extends radially outward sufficient to ensure an interference fir between itself and band 1 8 as hereinafter described.

In operation, the package of this invention is easily assembled. Container 30, after leaving the fill line, is sent to a capping station wherein closure 10 is screwed onto container 30 until a liquid-tight seal is achieved. Closure 10 at this stage will have a configuration wherein ribs 16 are nearly vertical and band 18 has a diameter which is preferably larger than the diameter of container thread 38. By having this relationship between diameters there is little or not interference from band 1 8 or ribs 1 6 as closure 10 is screwed onto container 30.

After closure 10 has been fitted to container 30, heat is applied to ribs 1 6 and band 18, as shown in Figure 4. Heat can be applied by blowing hot air, shown as HA in Figure 4, from blower H.

Ribs 1 6 and band 1 8 are of sufficient thinness so that they will soften and shrink inwardly upon cooling so that band 18 is in a position of interference under annular flange 34 as is shown in Figures 4 and 5. At this point band 18 will have a diameter substantially smaller than the outside of flange 34. Also, as seen in Figure 5, fracturable portions 20 will have a reduced cross-sectional area.

Any attempt to remove closure 10 from container 30 will result in axial movement of closure 10 thereby applying a stretching force to band 18 as it tries to expand over flange 34. When this occurs, at least one of fracturable portions 20 will fracture. Once fracture has occurred, the closure can be re-used but will always carry the telltale evidence of the first opening of the package.

Since ribs 1 6 do not fracture, band 1 8 will still be attached to closure 10 thereby obviating the problem of band 1 8 falling into the product as it is dispensed. Even though ribs 16 are shown to have an essentially rectangular shape, it is to be understood that they be shaped in any manner found conventient by the user of closure 10, e.g.

columnar shaped. Container flange 34 may also have different configurations, it only being important that the position of interference previously mentioned is achieved by band 18 with flange 34.

Claims

1. A thermoplastics material closure for fitment to a container having a neck with a means for removably attaching the closure to the container, which closure comprises a top wall, a side wall and an annular band attached to the sidewall by a plurality of spaced apart ribs, the band and ribs being heat-shrinkable upon the application of heat thereto and the band being so-structured that, upon said application of heat, after the closure has been fitted to the container, at least one region of reduced cross-sectional area is produced in the band as the band is shrunk around the container neck.

2. A closure as claimed in claim 1 and adapted for fitment to a container having an outwardly extending flange beneath means on the neck for removably attaching the closure to the container, the closure ribs being of sufficient length so that the band is below the flange when the closure is fitted to the container.

3. A closure as claimed in claim 1 or claim 2, wherein the sidewall has an inside surface bearing a thread for engagement with a thread on the container neck.

4. A closure as claimed in any one of claims 1 to 3, wherein a sealing liner is seated against the inside surface of the top wall.

5. A closure as claimed in any one of claims 1 to 3, wherein an annular sealing fin depends downwardly from the top wall.

6. A closure as claimed in any one of claims 1 to 5 made from polypropylene, polyethylene terephthalate or high density polyethylene.

7. A closure as claimed in any one of claims 1to 6, wherein the band is substantially uniform in cross-sectional area and has a plurality of regions of reduced strength, the positions of such regions alternating with the positions of the ribs and said regions having a reduced cross-sectional area after said application of heat after the closure has been fitted to the container.

8. A tamperproof closure for a container having a threaded neck or other means for attachment of the closure, the closure being of a heat-shrinkable thermoplastic material and having an upper portion including a top wall and a side wall having means for engaging the means for attachment of the closure and depending from the upper portion a plurality of ribs connected to an annular band having zones of reduced strength alternately located between the ribs, the band and ribs being shrinkable upon the application of heat to provide a position of interference fit under an annular protrusion on the container neck and the ribs being proportioned so as to be stronger than the reduced strength zones whereby preferential rupture occurs in the band upon disengagement from the container.

9. A closure substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 3, 5 and 6 ot the accompanying drawings either when modified by Figure 4 of the accompanying drawings or when modified by Figure 7 of the accompanying drawings.

10. A combination of a closure as claimed in any one of claims 1 to 9 and a container to which the closure is fitted.

11. A combination as claimed in claim 10, wherein the container comprises a body portion, a neck portion having means for removably attaching the closure and an outwardly extending flange beneath said attaching means on the neck, the closure being of sufficient length so that the closure band is below the flange and the band and ribs having been shrunk by the application of heat thereto so that the band nests in a position of interference under the flange.

12. A combination as claimed in claim 1 O or claim 11 , wherein the container is made from polypropylene or polyethylene terephthalate or glass.

13. A process for forming a closure as claimed in claim 1, by injection molding which comprises injecting molten thermoplastics material into a mold, the interior of which corresponds in shape to the desired closure, so that plastics material fill the top wall-shaped cavity and moves down to fill the sidewall-shaped cavity, the rib-shaped cavities and finally the band-shaped cavity, allowing the plastics material to set and removing the resulting closure from the mold.