EP0529383B1 - Plastic screw cap for pressurized bottles - Google Patents

Description

The present invention relates to a plastic screw cap for bottles, in particular for pressurized beverage bottles, consisting of a basic cylindrical shell with an internal thread and an essentially circular disc-shaped top plate, on the inside of which a thin, annular sealing strip is integrally formed and at the transition to the cylindrical one On the inside of the jacket, a bead is provided for pressing the sealing strip onto the upper, outer edge of the mouth of the bottle neck, the bead having an inner wall which is concentric with the closure axis and at least partially cylindrical, the diameter of which is slightly larger than the outer diameter of the upper edge of the bottle neck.

Such a closure is known from EP-A-0 114 127. In the known closure, two sealing strips which run obliquely to the closure axis are provided both on the inside and on the outside, which form a V-shaped opening into which the edge of the bottle neck engages when the closure is screwed on. Due to the V-shaped inclination of the two sealing strips, they are screwed onto the Bottleneck pressed essentially vertically upwards and folded away, whereby they lie more or less tightly against the bottle neck and are pressed into the free spaces provided on both sides of the sealing strips. The bottom of the V-shaped opening of the two sealing strips protrudes somewhat from the surface of the head plate, so that the further screwing on and pressing together of the sealing strips is limited by the engagement of this base with the upper edge of the bottle neck.

From US-A-4,623,070 a closure is known which also has the features of the preamble of claim 1. In this case, the sealing strip runs essentially along a conical surface which is strongly inclined to the axis of the closure. The edge of the bottle neck captures this sealing strip along the conical surface from below and also essentially pushes it upwards into a space provided in the head plate.

A similar closure is also known from EP-A1-293.901. In this closure, the bead has a substantially triangular cross section with a correspondingly tapering inner wall towards the top plate, parallel to which extends a conical sealing strip which, when the closure is screwed onto a bottle neck, lies on the upper outer edge of the bottle neck mouth and from the conical inner surface of the sealing bead is pressed. The approach of the conical sealing strip on the head plate is relatively far inward in the radial direction and is essentially flush with the cylindrical inner edge of the bottle neck. Only the outer end of the conical sealing strip is clamped between the conical inner surface of the bead and the transition from the end face of the bottle neck to its cylindrical outside, which is rounded in this area.

With carbonated beverages, there is a considerable overpressure of a few bars in bottles depending on the temperature and transport conditions. The top plate of the screw cap, which is made of elastic plastic material, bulges upward and thus also more or less lifts the shoulder of the sealing strip, so that its free end can be at least partially pulled out of the pinched area. A tight seal is no longer guaranteed in all cases. The tightness of the known closure is also impaired by the fact that, when the closure is screwed on, the sealing strip rests on the end face of the bottle neck, there being still considerable free space above this sealing strip. In the event of overpressure, the relatively thin and easily movable sealing strip, which is only clamped between the bottle neck and the bead at its outer end, is separated from it by the pressurized gas or liquid Bottle neck lifted off and pressed in the direction of this free space, whereby the free end can also slide out of the pinched area.

In addition, further plastic closures are known in the prior art, which provide a separate sealing washer or a separate sealing ring instead of an integrally molded sealing strip, which is inserted into the closure before the closure is screwed on. Such a closure design is more complex and expensive, and because of the widespread use of such bottles and correspondingly high turnover figures, even small penny amounts can make a noticeable difference in costs.

The known closures all have the disadvantage that the sealing strips, insofar as they are present, are essentially only pushed upwards and pressed together due to their more or less conical shape when they engage the bottle neck.

This does not always ensure sufficient tightness if the closure is not screwed onto the bottle neck with sufficient force. While the screwing on with sufficient force after filling the bottles with suitable machines can still be ensured relatively well, this is not always guaranteed for the consumer, especially since it often disturbs the consumer when he has to open such a bottle with considerable effort, which in particular less powerful people is sometimes only possible by using additional tools such as pliers and the like. In this respect, there is still a need for a closure, the tightness of which is ensured even if the closure is only screwed on by hand with a small force compared to mechanical closure. Therefore, the present invention has for its object to provide a plastic screw cap with the features mentioned, the tightness is guaranteed even with considerable excess pressure in a bottle even if the closure is screwed on only by hand with normal effort.

This object is achieved in that the sealing strip is also essentially cylindrical, the outer diameter of the sealing strip being approximately equal to the outer diameter of the bottle neck edge, and in that a circumferential groove is provided in the top plate on both sides of the sealing strip.

The sealing strip is thus attached to the top plate in such a way that (when the closure is attached) it runs near the outside of the cylindrical edge of the bottle neck and also close to the bead.

Through the combination of features according to the invention, i.e. in particular by the cylindrical design of the sealing strip, the outer diameter of which corresponds almost to the outer diameter of the edge of the bottle neck and by the provision of the two grooves in the top plate, in conjunction with the outer rounding which is generally present on all edges of the bottle neck, the sealing strip becomes itself when the closure is screwed on not only presses on the edge of the bottle neck, but rather slides on the edge of the bottle neck while stretching.

This configuration thus leads to the fact that the sealing strip between the bead and bottle neck is not only clamped in the region of the rounded transition, but is further drawn into the annular gap between the cylindrical outer wall of the bottle neck and the cylindrical inner wall of the bead. When the closure is put on or screwed on, more precisely when the sealing strip slides onto the upper end of the bottle neck, the essentially cylindrical sealing strip is first widened somewhat, thereby being gripped by the bead on its outside and then getting into a more or less flowing state, when it is pulled through the bead into the narrow annular gap between the bead and the bottle neck. In addition, because the sealing strip attaches to the head plate further out in the radial direction than in the known closure, bulging of the head plate in its central region practically no longer has any effect on the sealing strip and even a slight lifting of the head plate also in its outer region which of the sealing strips does not yet result in the sealing strip being pulled out of the annular gap since it projects relatively far into it and is clamped over a large area between the bead and the bottle neck. The sealing strip is hardly on the front of the bottle neck, but only in the rounded part and on the cylindrical part of the bottle neck where the sealing effect is to be achieved. Thus, the sealing strip in the radial direction within the sealing area has no significant contact surface for the pressurized gases or liquids inside the bottle and, moreover, also has no appreciable free space on the rear side of such a contact surface, so that the sealing strip is also lifted and pulled out is effectively prevented. The grooves provided on both sides of the sealing strip in the head plate contribute in this context to the fact that the sealing strip is sufficiently movable and is drawn directly and over the bottle neck edge until the end of the closing process, which is defined by the striking of the bottle neck edge on the head plate.

So that the sealing strip slides even better over the outer upper edge of the bottle neck when screwing on, in the preferred embodiment of the invention, a beveling of the inner edge of the free end of the sealing strip is provided.

An embodiment of the invention is preferred in which the transition of the cylindrical inner surface of the bead to the plane of the inner surface of the head plate takes place along a transition surface, the curvature of which corresponds to the curvature of the transition surface from the cylindrical outer surface to the end face of the end of the bottle neck.

This avoids almost any free space on the outside of the sealing strip, which - with the cap firmly screwed on - is absolutely fixed and can no longer be lifted off the bottle neck due to the internal pressure in the bottle.

In the preferred embodiment of the invention it is further provided that the inside diameter of the cylindrical wall of the bead is less than or equal to the sum of the outside diameter of the cylindrical wall of the upper edge of the bottle neck plus the thickness of the sealing strip in its main part. The sealing strip is thereby securely drawn into the annular gap between the inner wall of the bead and the outer wall of the bottle neck and more or less clamped there.

Figur 1

einen Teilquerschnitt durch einen teilweise auf einen Flaschenhals aufgeschraubten Deckel gemäß einer ersten Ausführungsform der Erfindung,

Figur 2

eine Ansicht entsprechend Figur 1 mit fast vollständig aufgeschraubtem Deckel,

Figur 3

eine zweite Ausführungsform in einer Ansicht entsprechend Figur 1,

Figur 4

die Ausführungsform nach Figur 3 mit vollständig aufgeschraubtem Deckel,

Figur 5

eine Ansicht entsprechend Figur 1 für eine dritte Ausführungsform und

Figur 6

die Ausführungsform nach Figur 5 mit vollständig aufgeschraubtem Deckel.

Further advantages, features and possible uses of the present invention will become clear from the following description of a preferred embodiment and the associated figures. Show it:

Figure 1

2 shows a partial cross section through a lid partially screwed onto a bottle neck according to a first embodiment of the invention,

Figure 2

2 shows a view corresponding to FIG. 1 with the lid almost completely screwed on,

Figure 3

2 shows a second embodiment in a view corresponding to FIG. 1,

Figure 4

3 the embodiment according to FIG. 3 with the cover fully screwed on,

Figure 5

a view corresponding to Figure 1 for a third embodiment and

Figure 6

the embodiment of Figure 5 with the cover fully screwed on.

The figures are merely schematic representations and do not necessarily reflect all proportions and dimensions to scale. As far as the relative position and dimensions of individual elements are particularly important for the present invention, this is emphasized accordingly.

FIG. 1 is a section along a plane which contains the axis (not shown) of the screw cap, which essentially also coincides with the axis of the bottle neck 7. Shown is a part of the essentially cylindrical shell 1 with threads 1a, part of the circular disk-shaped head plate 2, and the transition between these two parts with the sealing strip 3 and the bead 4. The threads 1a engage in corresponding threads 12 on the outside of the bottle neck 7 a.

The end of the bottle neck 7 has essentially the shape of a hollow cylinder with a flat, annular end face 8c, an outer cylinder jacket surface 8a and a rounded transition 8b between said surfaces. The production of such bottles means that it is not the end face 8c, but rather the faces 8b and 8a that are the most precisely defined areas of the bottle neck with the smallest tolerance deviations. For this reason, it is expedient to provide the seal of the plastic closure exactly in this area.

As can be seen in FIG. 1, the sealing strip 3 attaches to the inner surface 2a of the head plate 2 relatively far out in the radial direction. The attachment area of the sealing strip 3 has approximately the same outer diameter as the bottle neck and is thus so far that the sealing strip practically only on the areas 8a and 8b of the bottle neck when screwing onto the bottle neck, but not or only to a small extent on the end face 8c of the bottle neck comes to rest.

The bevel 11 on the inner edge of the free end of the sealing strip 3 ensures that when the closure is screwed onto the bottle neck 7, the sealing strip 3 slides out onto the bottle neck in the area 8b and 8a. The bead 4 ensures that the sealing strip 3 comes to rest firmly and sealingly on the surfaces 8a and 8b of the bottle neck by being clamped between the bead 4 and bottle neck 7. During the Unscrewing the free end of the in practice very thin and elastic sealing strip 3 to the outside and comes into contact with the more or less rounded edge 5 of the bead 4, so that this edge 5 takes the sealing strip with the further screwing and around the bottle neck pulling around and down. The width of the annular gap between the cylindrical inner wall 6 of the bead and the outer wall 8a of the bottle neck corresponds to the thickness d of the sealing strip 3 above the bevel 11 or is somewhat smaller in order to achieve a clamping effect.

Figure 2 shows the screw cap in the largely unscrewed state.

In contrast to the known embodiment with a tapered inner wall of the bead 4, the cylindrical inner wall of the bead 4 according to the present invention allows the plastic closure to be screwed onto the bottle neck to such an extent that the sealing strip 3 moves a considerable amount into the annular gap between the bottle neck 7 and the bead 4 is drawn in and thus effectively seals the bottle, even if the head plate 2 bulges or if the sealing strip 3 is pressed radially outside of the sealing area in its attachment area by the internal overpressure into the remaining free space. It can be seen in FIG. 2 that even in this state, in which the plastic closure has not yet been completely screwed onto the bottle neck 7, pressing the sealing strip 3 into the free space 13 would not impair the sealing function of the closure, since a substantial part is still present of the sealing strip 3 fills the annular gap between the bead 4 and the bottle neck 7.

FIG. 3 shows a slightly modified embodiment of the invention with a somewhat thicker head plate 2, the transition between the bead 4 and the head plate 2 also being less rounded. As can be seen in FIG. 4, an effective seal is guaranteed at all times in this embodiment. The closure can be screwed onto a bottle neck 7 to such an extent that the head plate 2 comes to lie completely on the end face 8c of the bottle neck 7, the sealing taking place in the area of the area 8a and especially in the area of the area 8b. The bead 4 in turn pulls the sealing strip 3 far into the annular gap between the bead 4 and the outer cylindrical surface 8a of the bottle neck 7. The lower inner edge 5 of the bead 4 is slightly rounded.

The annular grooves 9 and 10 also ensure sufficient mobility of the sealing strip 3 itself in the position in which the head plate 2 almost or completely touches the end face 8c of the bottle neck 7. Nevertheless you can see from the representation in FIG. 4 shows that the sealing strip offers only a minimal contact surface towards the pressure side (on the right in FIG. 4), so that there is no need to fear that the sealing strip 3 will be lifted off the sealing surface 8b even in the case of a relatively high overpressure.

The last-mentioned danger is completely eliminated by the embodiment shown in FIGS. 5 and 6. As can be seen in Figure 5, this embodiment differs from the two aforementioned embodiments essentially in that the cylindrical inner wall of the bead is somewhat shortened in the axial direction and in the form of a curved arc (in the cross-sectional view) in the plane of the inner surface 2a of the Head plate 2 merges, the curvature of this arc essentially corresponding to the curvature of the surface 8b of the bottle neck 7.

As can be seen in FIG. 6, this leads to the fact that when the closure is completely screwed on, on the side of the sealing strip 3 facing away from the inside of the bottle, there is practically no space whatsoever into which the sealing strip could be pressed if excess pressure occurs. The tightness of such a closure is thus ensured in all practically occurring cases and for all pressure ranges for which such closures are provided at all.

From the representation of the above embodiments, it can be seen that a difference to the known screw closure also consists in the fact that the sealing strip is clamped in the sealing area between a conical and a (partially) toroidal surface. Reaching this clamping position forms a kind of stop against further unscrewing. In contrast to this, in the present invention the sealing strip is pulled from the bead 4 more or less around the partially toroidal surface 8b and is held in this position in a sealing manner, only when the head plate is placed on the end face 8c of the bottle neck 7 forming a stop. In this position, the sealing strip offers the pressurized interior of the bottle only a very small contact surface and this only in the vicinity of the comparatively stiff attachment area of the sealing strip. Since a relatively long section of the sealing strip is pulled around the sealing surface 8b and not only the outermost end of the sealing strip 3 is clamped in, manufacturing tolerances of the bead and the bottle neck can also be handled more easily without disadvantage, since even if such tolerance deviations occur, part of the sealing strip is always present will rest on the sealing surface 8b.

The essentially cylindrical shape of the sealing strip 3 facilitates the manufacture of the closure, which is easier to demold than a closure with a conical sealing strip.

Claims (4)

1. Plastics screw closure for bottles, in particular for pressurised drinks bottles, composed of a basically cylindrical wall (1) with an internal thread (1a) and a substantially circular disc-shaped top plate (2), on the inside (2a) of which a thin annular sealing strip (3) is integrally moulded and at its junction with the cylindrical wall (1) there is provided on the inside a raised part (4) for pressing the sealing strip (3) against the upper, outer edge (8a,b) of a bottle neck (7), wherein the raised part (4) is provided with an at least partially cylindrical inner wall (6) concentric to the axis of the closure, the diameter of which is slightly larger than the external diameter of the upper edge (8a) of the bottle neck, characterised in that the sealing strip (3) is configured substantially cylindrically, the external diameter of the sealing strip is approximately equal to the external diameter of the edge of the bottle neck, and that on both sides of the sealing strip (3) there is provided a continuous groove (9, 10) in the top plate (2).
2. Plastics screw closure according to claim 1, characterised in that the inside edge of the free end of the sealing strip (3) is provided with an inclined part (11).
3. Plastics screw closure according to one of claims 1 or 2, characterised in that the transition of the cylindrical inside surface (6) of the raised part and the plane of the internal surface (2a) of the top plate (2) is along a transitional surface, the curvature of which corresponds to the curvature of the transition surface (8b) of the cylindrical external surface (8a) and the end face (8c) of the end of the bottle neck (7).
4. Plastics screw closure according to one of claims 1 to 3, characterised in that the diameter of the cylindrical internal wall (6) of the raised part (4) is smaller or equal to the sum of the diameter of the cylindrical external wall (8a) of the upper edge of the bottle neck plus the thickness (d) of the main part of the sealing strip (3).

Images