EP1545998A1

EP1545998A1 - Screw cap for pressurised containers

Info

Publication number: EP1545998A1
Application number: EP03770880A
Authority: EP
Inventors: Okten Gassner
Original assignee: Bericap GmbH and Co KG
Current assignee: Bericap GmbH and Co KG
Priority date: 2002-09-30
Filing date: 2003-09-24
Publication date: 2005-06-29
Anticipated expiration: 2023-09-24
Also published as: WO2004031045A1; US20050247663A1; ZA200501878B; RU2005113687A; PL374268A1; CA2496832A1; ATE398583T1; BR0314806A; EP1545998B1; AU2003280289A1; DE50310013D1; DE10245595A1

Abstract

The invention relates to a screw cap for containers with a threaded neck, in particular PET bottles designed to hold beverages containing CO<SUB>2</SUB>. Said cap comprises a top plate ( 1 ), an approximately cylindrical cap jacket ( 2 ), provided with an interior thread ( 3 ), an approximately cylindrical inner sealing collar ( 4 ), emanating from the top plate ( 1 ) and having an annular continuous region that projects radially outwards and an essentially cylindrical outer sealing collar ( 5 ), which concentrically surrounds the inner sealing collar ( 4 ). The maximum outer radius of the inner sealing collar and the minimum inner radius of the outer sealing collar differ only slightly, preferably by less than 2 mm and in particular by less than 1 mm and the inner and outer sealing collars ( 4, 5 ) are designed to receive the upper region of a bottle neck ( 11 ) in the annular gap formed between said collars. The aim of the invention is to provide a screw cap, which in general retains the excellent sealing properties of the known screw cap, even in extreme environmental conditions and is at the same time capable of limiting the pressures that occur in a container with a screw cap, without losing its sealing function. To achieve this, the cap is provided with devices ( 6, 7 ), which limit the axial depth of penetration of the edge of a bottle neck ( 11 ) into the gap between the inner ( 4 ) and the outer sealing collar ( 5 ).

Description

Screw cap for pressurized containers

The present invention relates to a screw cap for containers with a threaded neck, in particular for PET bottles, which are designed for receiving CO ₂ -containing drinks, with a head plate, an approximately cylindrical cap jacket with an internal thread, an inner one, starting from the head plate, and in approximately cylindrical sealing web, which has an annular circumferential, radially outwardly projecting area, and with an outer, substantially cylindrical sealing web, which concentrically surrounds the inner sealing web, the maximum outer radius of the inner sealing web and the minimal inner radius of the outer sealing web being only slightly and preferably differ by less than 2 mm and in particular by less than 1 mm and are designed to sealingly accommodate the upper region of a bottle neck in the intermediate space thus formed.

Such a screw cap is already known from European patent application No. 98 909 299, which goes back to the same applicant as the present application.

This known closure shows excellent sealing properties, which have led to considerable market success. A further improvement of the sealing effect hardly seems possible with justifiable means and is also not aimed at by the present invention. Rather, the screw cap according to the present invention essentially uses the same sealing principle, which is the combination of an inner seal by a radially inner sealing web, the cross section of which resembles an olive and which is therefore also referred to as a "sealing olive", in combination with a cylindrical one , outer sealing web originates, the special geometry of the two sealing webs and also other elements provided on the closure in combination with each other achieving the special sealing effect.

The known screw cap is usually used for closing PET bottles that contain carbonated drinks. These PET bottles and in particular their threaded necks are standardized and there are only a few standard types which are relatively similar overall, although the respective closures of the corresponding closures are precisely adapted to one of these standard types.

The wall thickness of the bottle neck edge of such PET bottles is usually less than 2 and often also less than 1.5 mm, for example 1.2 mm. In order to achieve a sufficient sealing effect, the maximum outer radius of the inner sealing web must be significantly larger, i.e. by at least 0.3 to 0.5 mm, than the inner radius of the edge of the bottle neck against which the inner sealing web lies sealingly. At the same time, the inner radius of the outer sealing web must Lich, that is usually 0.5 mm or more, smaller than the outer radius of the edge of the bottle neck, on which the outer sealing web lies sealingly. This means that the space between the inner web and the outer web is relatively narrow and has typical radial dimensions of only 0.5 mm. Depending on the wall thickness of the bottle neck rim, it can of course also be larger or somewhat smaller.

At the same time, a bead is also generally provided at a distance surrounding the outer sealing web, the inner radius of which is greater than the outer diameter of the bottle neck edge by less than the thickness of the outer sealing web, which means that the outer sealing web between the bottle neck edge and the screwed-on closure the bead is pressed together or pressed against the bottle neck by the bead and thereby contributes to the good seal. The inner sealing web also fulfills a centering effect, whereby only the interaction of all elements of the closure guarantees a surprisingly drastic improvement in the sealing properties.

However, these excellent sealing properties of the known closure, which the present invention also makes use of, can also have a disadvantageous effect under extreme conditions. For example, at extremely high outside temperatures, especially when corresponding filled bottles are exposed to direct sunlight and in connection with a particularly high carbon dioxide content dissolved in the liquid or a beverage, extremely high pressures can develop in such a PET bottle , This leads to a very heavy load on both the bottle and the cap and also a clearly visible bulging of the bottle body. It therefore appears desirable to avoid these extremely high pressures, particularly in PET beverage bottles.

In view of the above-described prior art, the present invention is therefore based on the object of providing a screw cap which, on the one hand, maintains the excellent sealing properties of the known screw cap in general even under very harsh external conditions, but which at the same time is also able without loss the sealing function to limit the pressures occurring in a container sealed with the screw cap.

This object is achieved in that devices are provided on the screw cap which limit the axial depth of penetration of a bottle neck edge into the space between the inner and the outer sealing web, independently of that caused solely by the sealing webs or the bottom of the space Limiting this penetration of the bottle neck edge into the space. The devices according to the invention, which act as an axial stop for a bottle neck onto which the cap is screwed, also have an advantageous effect with regard to the mechanical attachment of the closures, regardless of their influence on a reduction in the internal pressure in a bottle. When mechanically screwing on the closure from which the present invention is based, it may happen that the closure twists when screwed on or an annular bead, which can be provided outside the outer sealing web, is seated on the upper thread. The latter is particularly undesirable if the upper thread is not designed for such attachment, but rather has its upper end inclined to the closure axis. In this case, the closure can tilt. Since the webs according to the invention are now provided between the inner and the outer sealing strips, they act as an axial stop which, when the closure is screwed onto a bottle neck, immediately leads to a sharp increase in the torque as soon as the end face of the bottle neck reaches the webs. It is understood that any cylindrical bead outside the outer sealing strip is designed so that it does not come into contact with the thread before the end face of the bottle neck reaches the webs mentioned.

Basically, a statically measured torque is set on capping machines for each capping head, which is determined in corresponding tests for the capping type concerned. During the closing process, however, due to the kinetic energy of the fast rotating closing head to be braked, an additional torque arises, which can also be taken into account, but which varies with the mostly unavoidable fluctuations in the line speed, so that to achieve a sufficiently high torque even with slow speed A correspondingly high torque value is set for machines, which in turn can easily lead to overtightening of the fastener in the case of high-speed machines. The torque that occurs when the cap is overtightened is also referred to in technical terms with the English term "strip-torque".

It has been found that the webs according to the invention noticeably increase this torque, which is required for overtightening the closure, which consequently contributes to the fact that overtightening can be avoided even when setting comparatively high static torque values. In addition, the sharp increase in torque which occurs when the bottle neck meets the webs according to the invention can be used to control the machine in order to end the unscrewing process when such an increase begins.

Even if you do not want to set the tightness or overpressure safety of the closure by the measures according to the invention or the mentioned ventilation effect does not occur due to the design of the seals, the webs according to the invention are under the face point of an improvement in the properties when mechanically screwing on the closures nevertheless makes sense with regard to the above-mentioned overtorque.

The devices are expediently designed in such a way that a distance of between 0.5 and 1.5 mm remains between the plane defined by the inner surface of the head plate and the plane defined by the upper edge of the bottle neck, provided in this connection is that the reason for the space between the sealing webs, which is the actual reference point for the axial position of the bottle neck edge, lies approximately in the inner plane of the head plate. If this is not the case, the corresponding distance should better be determined relative to the plane defined by the reason for this intermediate space.

In the preferred embodiment of the present invention, the devices for limiting the penetration of the bottle neck edge into the intermediate space between the sealing webs consist of elevations or webs which extend from the base of the intermediate space into the intermediate space. In this way, these elevations or webs when the cap is screwed onto a bottle neck form stops for the bottle neck edge, which prevent further penetration of the bottle neck edge into the space between the sealing webs. Due to the material and their dimensions, these stops are not rigid, but to a certain extent are elastically flexible. It has proven to be expedient if the webs or elevations have an axial height (measured in each case from the bottom of the intermediate space) between 0.3 and 2.5 mm, preferably in the range from 0.5 to 1.8 mm to have.

The portion of the head plate between the sealing webs at its lowest point is referred to as the reason for the intermediate space.

The width of the webs should be sufficient in the circumferential direction so that they can act as stops and in turn cannot be excessively elastically deformed and pressed in. A width of the webs of 0.3 to 2 mm has proven to be useful for this.

In the preferred embodiment, a plurality of webs are distributed at approximately equal angular intervals along the annular space. For example, in the preferred embodiment of the invention, six webs are each arranged in the intermediate space at angular intervals of approximately 60 ° and extend in the axial direction into the intermediate space by approximately 1.5 to 1.8 mm from the deepest bottom of the intermediate space. )

for the rest, it has also proven to be expedient if the wall thickness of the head plate in the area of the intermediate space, more precisely the minimum wall thickness of the head plate in this area, is somewhat less than the wall thickness of the head plate in the rest of the area, that is to say in particular in the area immediately inside of the inner sealing web. The top plate has more typical have a largely constant wall thickness of the order of 0.8 to 2.5 mm, mostly between 1 and 1.5 mm and can have, for example, an additional reinforcement or bulge in the center. The (minimum) wall thickness of the head plate in the space between the sealing webs is expediently 10 to 50%, preferably about 20 to 40% less than radially inside the inner sealing web.

According to an alternative embodiment of the invention, the devices for limiting the penetration of the bottle neck edge into the space between the inner and outer sealing webs are not between these sealing webs, but e.g. provided radially outside the sealing webs. For this purpose, a bead lying radially outside the outer sealing web can be provided and designed such that it is designed as a more or less elastic stop for the upper thread edge of a bottle neck thread, the stop face of the bead, which runs essentially in a plane perpendicular to the screw cap, has an axial distance from the bottom of the intermediate space which is larger by 0.3 to 2 mm, preferably 0.5 to 1.5 mm, than the axial distance of the upper thread edge from the upper edge surface of the threaded neck of a bottle for which the screw cap is provided.

Such an embodiment is particularly suitable for bottle necks, the threads of which run out over a considerable circumferential section in a plane perpendicular to the axis of the bottle neck. With such a thread, the upper, flattened thread edge lies against a correspondingly large circumferential section on the stop surface of the bead, so that this also ensures a clearly defined axial position of the edge of the bottle neck between the two sealing strips. Due to the fact that either the thread edge on the stop surface of a bead or the bottle neck edge directly on the web surfaces between the sealing webs, the bottle neck edge penetrates less deeply between the two sealing webs than would be possible without corresponding stops, the elasticity of the stops still giving a certain freedom of movement so that the exact axial position of the bottle neck between the sealing webs in the closure can still be adjusted by tightening it more or less or by rotating the cap thread relative to the bottle neck thread within certain small limits.

In the conventional closure, the penetration of the edge of the bottle neck was essentially limited by the fact that the space between the two sealing webs tapered towards the head plate and thus effectively formed a resistance for the wide insertion of the bottle neck edge. The top edge of the bottle neck could reach a position that was very close to the inner plane of the head plate or close to the bottom of the space between the sealing webs. Due to the dimensions of the invention, the bottle neck edge is kept in the axial direction of the order of 1 mm from the inner plane of the head plate, and a little further from the bottom of the space between the two Sealing webs, provided that the head plate is somewhat thinner in the area of this base than in the rest of the head plate, the base of this intermediate space is thus additionally set back somewhat from the inner plane of the head plate. Of course, the position with respect to the inner plane of the head plate can deviate more from the specified dimensions if the thickness of the head plate is changed. The point of reference is ultimately the reason for the space mentioned.

The sealing engagement of the edge of the bottle neck with the two sealing webs remains essentially the same as in the known closure, but the sealing webs - especially near their attachment to the head plate - are spread a little less than if the bottle neck edge were to be pushed in deeper the space can penetrate to where the space already tapers significantly, so that in this area in particular the outer sealing web is put under even greater tension and thus seals even better.

The design according to the invention means that from a certain internal pressure in a container, which can reach a range significantly above 7 bar, for example due to excessively high temperatures, some gas can escape from the bottle neck and between the bottle neck edge and sealing webs until the pressure is sufficient again (specifically, for example, to a value slightly above 7 bar). The closure according to the invention thus ensures that a sufficient and desired overpressure is always maintained in the container and only an excessively strong overpressure is reduced. At most, this leads to a slight degassing of excess carbonic acid, especially if excessive carbonic acid was dissolved in the liquid. However, because a sufficient overpressure is always maintained, complete or extensive CO ₂ degassing of the liquid is prevented.

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

1 shows a view in the axial direction from the inside of a closure cap according to the invention, FIG. 2 shows a section containing the axis through the closure cap shown in FIG. 1, FIG. 3 shows an enlarged section of the closure cap according to FIG. 1, FIG. 4 shows a part in section and on a Bottle neck screwed on

5 and an enlarged detail of the encircled area in FIG. 4. One can see in FIGS. 1 to 3 a closure cap, generally designated 10, which essentially consists of a head plate 1 (also called the cap base) and a cap jacket 2. The cap jacket has an internal thread 3 and on its lower edge a tear-off band, which serves as a guarantee element and the condition of which can be seen whether the closure has already been opened. This tear-off tape is known per se and is of no importance for the present invention, so that it is not described in more detail here.

Two ring-shaped sealing webs 4 and 5 extend inward from the head plate in the axial direction. The radially inner sealing web is somewhat more solid and also axially longer than the radially outer sealing web 4. The maximum thickness of the inner sealing web is e.g. 1 to 1.5 mm and its minimum thickness is of the order of 0.8 mm, in particular the free lower edge being chamfered on its outside, which should facilitate the sliding of the inner sealing web 4 into a bottle neck. Due to the approximately olive-shaped cross-section of the sealing web 4, at least on its outside, this sealing web is also referred to below as a "sealing olive" in accordance with what has become common in the meantime. Radially outside the ring-shaped sealing olive 4, an approximately cylindrical and somewhat thinner sealing web 5 can be seen, the free end of which is slightly chamfered and rounded on the inside, which in turn is intended to facilitate the easier sliding of the outer sealing web 5 onto the edge of a bottle neck. The clear space between the inner and outer sealing web 4 and 5 is relatively narrow and is usually not significantly more than 1 mm or even less. The maximum radius of the inner sealing web differs even less from the minimum radius of the outer sealing web, the difference of which is typically only of the order of magnitude of 0.5 mm.

The space between the inner sealing web 4 and the outer sealing web 5 is designated by the reference number 9.

In Figure 3, the essential elements of the screw cap according to the invention just described can be seen again in an axial plan view of the interior of the screw cap 10. Radially from the inside out one recognizes the annular and somewhat thicker sealing web or the sealing olive 4, the space 9 directly radially outside the same and the sealing strip 5 immediately radially outside the space 9. The cap jacket 2 with the internal thread is connected to this on the outside 3 or the inner bead 7.

In the intermediate space 9, the webs 6 according to the invention can be seen both in FIG. 1 and in FIG. 3 at angular intervals of approximately 60 °. The sectional plane according to FIG. 2 runs straight through two opposite webs 6, so that the axial height of the webs is shown in FIG 6 is recognizable. FIG. 4 shows the closure cap 10 according to the invention and screwed onto a bottle neck up to the elastic stops. FIG. 5 shows a further enlarged detail from FIG. 4. Even if certain dimensions are not always important, it should be noted that the screw cap according to the invention is shown essentially to scale in the present figures, FIGS. 1, 2 and 4 showing the closure on a 2: 1 scale, FIG. 3 showing the closure on a 5: 1 scale and FIG. 5 showing the detail Figure 4 reproduced approximately on a scale of 10: 1 compared to the original closure. It can be seen from this that the thickness D of the head plate is approximately 1.5 mm, while the thickness d of the head plate at the deepest point of the base of the space 6 is somewhat less and is, for example, 1.1 to 1.4 mm. The thread 3 of the screw cap 2 is screwed onto the thread of the bottle neck 11, to the extent that the edge of the bottle neck has penetrated between the two sealing webs 4, 5, up to the stop on a web 6, of which a total of six stops 6 the circumference of the space 9 are evenly distributed. With 8 an external corrugation of the screw cap 10 is designated, which serves the firm and secure gripping of the screw cap when unscrewing and screwing on the screw cap.

Without the webs or stop elements 6, the bottle neck 11 could easily penetrate further into the intermediate space 9 by 0.5 to 1 mm, the outer sealing web 5 in particular being stretched and tensioned even more and thereby being even firmer and closer to the edge of the bottle neck anläge. The somewhat smaller wall thickness d of the head plate in the area of the intermediate space 9 also has the purpose of giving the head plate an additional elasticity and extensibility in this area, which also leads to the firm and tight engagement of the two inner and outer sealing webs 4, 5 contributes to the bottle neck rim.

The webs 6 ensure that this sealing engagement is retained on the one hand, but is not quite as strong as without the webs 6. This leads to an excessive overpressure in the bottle being reduced. Both the bottle itself and the closure are less stressed.

Even if, as already mentioned, compliance with the exact dimensions, as can be seen from the figures, does not appear to be necessary, it can nevertheless be assumed that the advantageous effects of the closure according to the invention are due to the fact that it is based on tolerance deviations of the bottle neck and also of the screw cap even reacted relatively insensitive. This is probably also due to the fact that this closure, in addition to the other geometric features as defined in the claims, is due to the material used (polyolefin) and the wall thicknesses of the sealing webs and the head plate in the area between the sealing webs, and the dimensions of the stop elements or webs has elastic properties which are particularly favorable for catching tolerance deviations, without the sealing function of the closure according to the invention being impaired and nevertheless giving in to the seal Pressures well above 7 bar is guaranteed. The relative dimensions of the screw cap elements listed above, as they result from the figures and the scales mentioned above, should therefore be maintained within a fluctuation range of + 20% if possible. However, other relative dimensions can be particularly useful and necessary if the principles of the present invention are applied to container closures in which the container necks have significantly different dimensions (in particular different diameters and wall thicknesses) than in the exemplary embodiments shown here.

Claims

Patent claims

1. screw cap for containers with a threaded neck, in particular for PET bottles, which are designed to hold drinks containing CO ₂ , with a head plate (1), an approximately cylindrical cap jacket (2) with an internal thread (3), an inner, from the top plate (1), approximately cylindrical sealing web (4), which has an annular circumferential, radially outwardly projecting area, and with an outer, substantially cylindrical sealing web (5), which concentrically surrounds the inner sealing web (4) , the maximum outer radius of the inner sealing web and the minimum inner radius of the outer sealing web differing only slightly and preferably by less than 2 mm, in particular less than 1 mm, and the inner and outer sealing webs (4, 5) are designed for this , to receive the upper region of a bottle neck (11) in the annular space formed between them, characterized in that E devices (6, 7) are provided which limit the axial depth of penetration of a bottle neck rim (11) into the space between the inner (4) and the outer sealing web (5).

2. Screw cap according to claim 1, characterized in that the devices are elevations or webs (6) which extend axially into the intermediate space (9) from the bottom of the intermediate space (9).

3. Screw cap according to claim 2, characterized in that the webs have an axial height between 0.3 and 2 mm, preferably from 0.5 to 1.2 mm.

4. Screw cap according to one of claims 2 or 3, characterized in that the webs have a (measured in the circumferential direction) width of 0.5 to 3 mm.

5. Screw cap according to one of claims 2 to 4, characterized in that the webs (6) are distributed at approximately equal angular intervals along the annular space (9).

6. Screw cap according to one of claims 2 to 5, characterized in that six webs are provided at angular intervals of approximately 60 °.

Screw cap according to one of claims 1 to 6, characterized in that an annular circumferential bead (7) is provided radially outside the outer sealing web (5), which is designed as a stop for the upper thread edge of a bottle neck thread, the stop face of the bead (7 ) from the bottom of the space (9) has an axial distance which is 0.3 to 2 mm, preferably 0.5 to 1, 2 mm larger than the axial distance of the upper thread edge from the upper edge surface of the threaded neck of a bottle for which the screw cap is provided.

8. Screw cap according to one of claims 1 to 7, characterized in that the wall thickness of the head plate in the area of the intermediate space (9) is less than in the area radially inside the inner sealing web (4).

9. Screw cap according to claim 8, characterized in that the wall thickness of the cap base in the area of the intermediate space (9) is 5 to 15%, preferably by about 10%, less than the wall thickness of the cap base in the area immediately radially inside Sealing web (4).