Plastic Sealing Screw Cap With Improved Tamper-Proof Strip

The invention relates to a plastic sealing screw cap with an improved tamper-proof strip. It is related to the technical field of packaging elements.

Numerous sealing screw devices having a safety means intended to control access to the contents are known of the container closed by these devices, and to prevent, in particular, fraudulent handling of these contents.

Generally, these sealing devices which are fitted on bottles whose rings are of the almost universally standardized type known under the name "Pilferproof" have a screw cap, possibly provided with a seal, and an annular safety strip that can be separated at the lower part from the skirt of the cap. Any attempt to unscrew the cap must cause the separation of the safety strip.

Originally, these tamper-proof caps were made of metal, particularly aluminum and, after screwing on the cap, the safety strip was crimped on the neck by a simple mechanical device.

At the present time, there is a tendency to replace aluminum with thermoplastic polymers which are no longer suited to a simple crimping because of their natural elasticity,

Therefore, a certain number of solutions have been devised to provide a crimping of the tamper-proof strip.

In French Pat. Nos. 2,282,378 and 2,467,790, heat-shrinking of the tamper-proof strip under the action of the jet of hot air is performed.

This solution involves adding an additional stage to the bottling and capping lines, and exhibits the risk of total melting of the seals when the line stops, which necessitates providing a safety device. Further, the appearance of the shrunken strip often leaves something to be desired.

In French Pat. No. 2,349,140, the tamper-proof strip is folded toward the inside of the cap when it is screwed on the neck of a bottle, so that its upper edge strikes against a projection of the neck. During unscrewing, the strip thus locked cannot rise and is separated from the skirt. But there is a danger that the strip will be pulled out without separating.

This invention constitutes another solution of this problem, a solution which provides both an easy fitting of the cap and a clean and reliable separation of the tamper-proof strip during the first unscrewing.

Particular means for sealing the cap are proposed.

FIGS. 1 to 4 represent in section (FIGS. 1 and 2) or in partial section (FIGS. 3 and 4) the cap, the object of the invention. FIG. 3 also represents a first means for sealing the cap of the invention.

FIGS. 5 and 6 represent, in axial half-section, a second sealing means.

FIG. 7 represents, in axial half-section, a third sealing means.

The sealing screw cap of the invention has (FIG. 1) a head (1) and a skirt (2) provided with an inner threading (3) which works with the threading of the container to be sealed. At the lower part of the skirt (2) the tamper-proof strip (4) is fastened by a multiplicity of bridges (5) which constitute the breaking points during subsequent unscrewing. The tamper-proof strip (4) has a continuous annular upper part (4A) and a lower part consisting of a multiplicity of tabs such as (6) connected to the upper part (4A) by a thinner part (7) which constitutes a sort of hinge. The tabs (6) comprise a heel (8) and a thinner extension (9).

The tabs (6) are molded in the position of FIG. 1, i.e., turned upward. During removal from the mold, they turn and come into the vertical position as in FIG. 2. Once removal from the mold is completed, their own elasticity brings them into the position of FIG. 1, after pivoting around the thinner area (7) which acts as a hinge. Thus they form an acute angle with the annular part (4) and are turned toward the inside of the cap.

During the screwing of the cap over the glass ring (10) (FIGS. 3 and 4), the tabs (6) are forced by the counter-ring (11) of the neck to fold against the strip (4) and, at the end of screwing, the heels (8) go beyond the edge (12) of the counter-ring (11) (FIG. 3). The elastic memory of the tabs (6) then flattens the thinner extension (9) over the counter-ring (11) in such a position that any attempt at unscrewing causes the heels (8) to strike under the edge (12) of the counter-ring (11). The thinner extension (9) of the tab (6) being wedged between the strip (4A) and the counter-ring (11), the heels (8) cannot be disengaged downward, and the breaking of the bridges (5) is then inevitable, which leaves visible proof of this first opening of the cap.

This plastic sealing screw cap with an improved tamper-proof strip has, with this tamper-proof device, sealing means which, separately or in combination, constitute advantageous improvements of the cap.

A first sealing means is an inner lid (13) in the shape of a slanted peripheral lip (FIG. 3) whose outer surface is applied over the interior of the rounding of the end of the neck of the bottle during sealing by screwing on the cap.

A second sealing means (FIGS. 5 and 6) is particularly effective; it makes the seal on the inside of the neck a little lower than its opening thanks to a lid (14) connected to the head (1), this lid (14) being formed by a central sleeve in the shape of a skirt (15) flanked by a peripheral side lip (16). The outside diameter of the body of the central sleeve in the shape of a skirt (15) is slightly smaller than the minimum diameter provided for the inside (17) of the neck, the terms minimum and maximum meaning generally acknowledged limits for the inside diameter (17) because of the variations inherent in the industrial processes of bottle manufacturing. The outside diameter of the peripheral side lip (16) is slightly larger than the maximum provided for the inside (17), so that the end of the peripheral side lip (16) first strikes against the upper end of the neck when the cap is screwed on.

By way of example and to clarify the ideas, in the case of a neck with an inside diameter (17) in industrial practice between 16.7 mm and 19 mm, the sleeve (15) has an outside diameter of 16.3 mm and its peripheral lip (16) has an outside diameter of 19.5 mm.

During the screwing on of the cap, the lower part (18) of the sleeve penetrates with a slight play until the peripheral side lip (16) strikes against the edge of the neck (FIG. 5), then when the screwing is continued, the peripheral side lip (16) enters into the neck by swinging upward (FIG. 6), this swinging causing a flaring of the lower part (18) of the sleeve in the shape of a skirt (15), this lower part (18) then being applied lower on the inner surface of the neck. Thus, there is obtained a double sealing by the ends of the peripheral side lip (16) and the lower part (18). As can be seen in FIG. 6, this effect of swinging and flaring is reflected in each axial section of the lid by a rotation and a bending diagrammed by the arrow. In the case of a container containing a liquid under pressure, the inner pressure tends to apply the lower part (18) of the sleeve more against the inner wall of the neck, and the end of the peripheral side lip (16) continues to perform a second sealing, its application against the wall being due to its swinging and to its elasticity. The peripheral side lip (16) is preferably directed downward (FIG. 5), so as to emphasize this effect of swinging and elastic support.

A third sealing means (FIG. 7) performs the sealing on the area of the external surface of the neck between the rounding of the end of this neck and the beginning of the threading. A peripheral lip (19) connected to the skirt (2) of the cap above its threading extends inward so that it is applied rather strongly over the outer wall of the neck, in the area between the rounding of the end and the threading, an area whose diameter tolerances are quite narrow, when the cap is screwed on. When the cap is screwed on, the end of the peripheral lip (19) rests against the outer wall of the neck and turns upward by being applied elastically. The peripheral lip (19) at rest is directed preferably downward so as to increase this elastic effect or spring effect. The advantage of the location of this peripheral lip constituting the third sealing means is the good reproducibility of the quality of the sealing obtained linked with the narrow diameter tolerances of the application area.

The sealing screw cap of the invention, provided with sealing means and in particular with any one of the three means explained above or with a combination of any of these means is easily made by molding of a thermoplastic polymer such as polypropylene. Its tamper-proof device offers a total reliability and adapts completely to all the automatic bottling and capping lines. The cap of the invention fits on the containers without detracting from their esthetic quality.