EP0271768A1 - Deep-drawn aluminium screw closure for glass containers under pressure, and deep-drawing device for the manufacture of the top portion of such a closure - Google Patents

Abstract

A deep-drawn screw cap of aluminum for glass bottles under internal pressure, where the transition area between the upper end face 1 to the lateral thread face 2 up to now was always evenly deep-drawn, now is to have at least one undeformed partial area 8. Because of this, sealing against the lateral edge 7 of the mouth is partially disrupted and a chance for the escape of gas is purposely provided in case the internal pressure in the glass bottle should rise too high. If required, a plurality of such partial areas 8 may be provided. In the deep-drawing device for a sealing head for the production of such screw caps the inner recess 12 should provide at least one partial enlargement 14 oriented towards the center axis 13 and extending approximately to the diameter of the preceding recess 11.

Description

Technical field

The invention relates to a deep-drawn screw cap made of aluminum for glass bottles under internal pressure with an upper end surface, a lateral threaded surface and optionally a locking ring, with a sealing compound being arranged on the inside of the end surface, in particular close to the transition to the threaded surface, by means of which the deformed part Closure a seal is made along the edge of the mouth of a glass bottle. Furthermore, the invention relates to a deep-drawing device for a closure head for producing rotary closures made of aluminum for glass bottles under internal pressure with a die which can be plugged onto a blank from above and has a plurality of concentric recesses which become smaller from the outside inwards, the first recess being continuous from the outside tapered inside to approximately the largest outside diameter of the screw cap, followed by a second recess with a constant diameter and finally followed by a third recess with a smaller diameter, which is used to deep-draw the blank down to the side mouth of a glass bottle.

State of the art

When it comes to the closure technology of glass bottles with an external thread at the mouth, two types of screw caps are to be differentiated, namely liquid-tight screw caps, generally known as so-called pilferproof closures or PP caps, and gas-tight screw caps, also as GD closures known in practice. The former Closures are used for so-called still beverages, such as spirits. With this type of closure, the sealing takes place between the upper end face of the screw cap, which regularly carries the seal, and the upper rim of the mouth of the glass bottle. A sufficient contact pressure can be maintained through the effective thread, that is the external thread of the glass bottle in connection with the thread surface of the screw cap created by rolling. However, there is no gas-tight seal, rather that system can only be classified as liquid-tight.

Such closures are therefore unsuitable for carbonated drinks. These are usually under a pressure of several bar, for. B. 4 - 6 bar. This requires the gas-tight screw caps, in which an additional seal is made by deep-drawing the transition area between the upper sealing surface and the lateral threaded surface of the screw cap on the lateral mouth edge of the glass bottle. This system can be described as extremely tight and pressure-resistant. In view of the numerous carbonated drinks that are filled in this way and the basic suitability of also filling fruit juices according to this system, i.e. closing them, for reasons of economy (to avoid additional tool costs and changeover work) this technique is mostly used unchanged for fruit juices .

As can be seen, gas-tight screw caps are used in considerable quantities. Serious accidents can occur, even if only sporadically. Depending on the degree of emptying, one with a carbonated drink filled glass bottle and the instantaneous temperature influence can easily build up internal pressures, which exceed the internal pressure by several times during filling. This can cause the screw cap to lift off and "blow off" the glass bottle. The twist lock can be lifted extremely vehemently, even like a bullet, and is therefore quite dangerous. Still, it has to be called the lesser evil. The screw cap is not always the weakest point in such cases, but sometimes the glass bottle itself can no longer withstand such internal pressure. This usually leads to an explosive destruction of the glass bottle, which can lead to extremely dangerous injuries if people are present. This has been reported repeatedly in the press.

Fruit juice bottles with gas-tight screw caps are also a serious source of danger. Although fruit juices are usually filled hot and initially lead to a vacuum; In the case of fruit juices, however, fermentation can also cause an internal pressure to build up. This is all the more remarkable since glass bottles with a smaller wall thickness are often chosen for fruit juices. So there is also a considerable risk of injury there. - Other twist locks are also known specifically for fruit juices, namely with a circular punch in the middle of the upper end surface, which allows the limited central area to bend downwards as an indicator on the one hand when vacuum and on the other hand at an impermissibly high internal pressure along the punching line (as a predetermined breaking point ) to burst. However, these options do not work if in practice - as already mentioned, for reasons of cost - carbonated drinks and fruit juices are treated equally, that is, they are filled with the same machine without changes.

Presentation of the invention

In view of this practice and the associated disadvantages and in particular dangers, the invention has set itself the task of developing a twist lock of the type mentioned in such a way that the sealing effect is lost with certainty when higher internal pressures are exceeded. This should no longer allow impermissible internal pressures to build up. This should also apply to twist-off closures with the circlips that are common today, which up until now have favored the twist-lock closure to remain in place and thus an impermissible build-up of pressure when the glass bottles are not yet opened.

This object is achieved according to the invention in that at least one partial area at the transition from the end surface to the threaded surface is not deep-drawn down to the lateral mouth edge, but is rather excluded from such a deformation.

The invention is based on the knowledge that the deep-drawing of the transition area between the upper end face and the lateral thread surface certainly produces a high increase in tightness. The usual deformation for this, however, only allows the twist lock to act as a uniform sealing element. In contrast, the invention with its different shape now creates a local area of relatively low resistance and thus less tightness, which, if necessary, has the desired safety function. In view of the local changes and effects, one could also say that it is a safety function similar to a safety valve. Once the gas has overcome the reduced sealing distance in the undeformed section, it can run freely emerge from the twist lock via the otherwise permeable threads as well as the locking ring. It no longer matters whether the rotary lock is provided with a locking ring or not.

As can be seen, the invention therefore proposes a new shape which allows blowing off at a defined point without the overall locking device having to be lifted off or larger areas thereof being deformed. The larger the undeformed sub-area is selected, the more a blow-off can be expected. However, since, as a rule, not only the condition of a safe blow-off has to be fulfilled, but first of all a sufficient sealing effect, the ratio of the proposed undeformed partial area to the remaining area deformed in a known manner remains individual, depending on the glass thickness, filling material and other criteria determine. Suitable values can be determined empirically easily and reliably.

It is better than providing a single longer undeformed partial area, if necessary, to select several correspondingly shorter partial areas. The length of the partial areas should count according to millimeters, for example between 3 and 7 mm. It is also advantageous if the subregions are arranged in a uniform distribution along the lateral edge of the mouth. With the aforementioned measures, the somewhat opposite demands for high tightness and timely blowing can be reliably coordinated.

For a deep-drawing device of the type mentioned at the outset, the invention proposes that the third recess have at least one partial extension aligned parallel to the central axis up to approximately the diameter of the second recess. Furthermore, several extensions should be provided and the extensions should be evenly distributed around the central axis. Finally, an advantageous further development is characterized in that the extensions have an approximately semicircular cross section with a rounded outlet area in plan view.

The proposed deep-drawing device can easily be used instead of known deep-drawing devices in the closing heads of existing machines. It allows the desired twist locks to be manufactured quickly and effortlessly. It goes without saying that a stop (abutment) which can be pressed in against a spring or the like can be used in the third recess, in particular also a stop provided with an additional stylus, corresponding to the known so-called safety plungers.

Brief description of the drawing

• Fig. 1 einen erfindungsgemäßen Drehverschluß in Drauf­sicht,
• Fig. 2 den Gegenstand von Fig. 1 ohne Riffelung im Schnitt entlang der Linie II - II sowie, darin eingeblendet, die Mündung einer Glasflasche mit ihrem Außengewinde in Seitenansicht,
• Fig. 3. den unteren Teil einer erfindungsgemäßen Tiefziehvorrichtung im Längsschnitt und
• Fig. 4 den Gegenstand von Fig. 3 in Unteransicht.

The invention is described below with reference to the drawing for preferred exemplary embodiments. In it show:

• 1 is a top view of a twist lock according to the invention,
• 2 the object of FIG. 1 without corrugation in a section along the line II - II and, faded in, the mouth of a glass bottle with its external thread in a side view,
• Fig. 3. the lower part of a deep-drawing device according to the invention in longitudinal section and
• Fig. 4 shows the subject of Fig. 3 in bottom view.

1 and 2, a twist lock made of aluminum has an upper end face 1, a side threaded surface 2 and a locking ring 3. The upper end face 1 is essentially flat and undeformed, the lateral thread surface 2 corresponds to the external thread 4 at the mouth of the glass bottle to be closed, whereby it is brought into this shape by rolling, and the locking ring 3 is crimped inward as a kind of collar . On its inside, the end face 1 has a sealing compound 5, which extends to the inside of the threaded surface 2.

As can be seen, there is initially a seal between the end face 1 and the upper mouth edge 6 of the glass bottle. As far as the transition area between the upper end face 1 and the lateral threaded surface 2 is deep-drawn with contact pressure in the direction of the lateral mouth edge 7 of the glass bottle, there is an additional sealing effect. However, this is interrupted where partial areas 8 have remained undeformed according to the proposal of the invention. In the present case, there are four sub-areas, which are evenly distributed over the circumference of the screw cap and each measure less than 1 cm in length. As intended, gas leakage and pressure reduction occur in one or more of these areas if the internal pressure in the glass bottle should rise to dangerous levels. In this way, uncontrolled destruction with property damage and, above all, damage to health can be counteracted in good time. 3 and 4, a deep-drawing device has a die 9 with recesses 10, 11 and 12, which are arranged concentrically around a central axis 13 and become smaller from the outside inwards. Thus, the first recess 10 tapers continuously down to approximately the largest outside diameter of the twist lock to be produced. This is directly followed by the second recess 11 with an approximately constant diameter. In contrast, the third recess 12 is stepped, ie it has a smaller diameter, but which is also essentially constant.

According to the invention, the third recess 12 has partial extensions 14 aligned parallel to the central axis 13. These extend up to approximately the diameter of the second recess 11. In the present exemplary embodiment, four extensions 14 are arranged evenly distributed around the central axis 13. In plan view, they have an approximately semicircular cross section with rounded outlet areas 15. In the interior of the third recess 12, a stop (abutment) 16 is held displaceably, which can be pressed against the force of a compression spring 17 into the interior of the die 9.

The deep-drawing device described above can be used in conventional closing heads of automatic filling machines. It is moved from above onto a blank closure and causes the transition area between the upper end face and the lateral thread surface to be deformed, with the exception of short partial areas which remain undeformed, in accordance with the extensions 14.

Claims (7)

1. Deep-drawn screw cap made of aluminum for glass bottles under internal pressure with an upper end surface, a lateral threaded surface and optionally a locking ring, a sealing compound being arranged on the inside of the end surface, in particular close to the transition to the threaded surface, by means of which Completely deformed closure there is a seal along the edge of the mouth of a glass bottle, characterized in that at least a portion (8) at the transition from the end face (1) to the threaded surface (2) is not deep-drawn down to the side mouth edge (7), but rather one such deformation is excluded. 2. Twist lock according to claim 1, characterized in that a plurality of undeformed partial areas (8) are provided along the lateral mouth edge (7) of a glass bottle. 3. Twist lock according to claim 2, characterized in that the undeformed portions (8) are arranged in a uniform distribution along the lateral mouth edge (7). 4.Teif pulling device for a closure head for the production of aluminum screw caps for glass bottles under internal pressure with a die that can be plugged onto a blank from above with several concentric recesses that become smaller from the outside inwards, the first recess being continuous from the outside in to approximately tapered to the largest outside diameter of the screw cap, followed by a second recess with a constant diameter and finally followed by a third recess with a smaller diameter, which serves to deep-draw the blank down to the side mouth of a glass bottle, characterized in that the third recess (12) has at least one partial extension (14) aligned parallel to the central axis (13) up to approximately the diameter of the second recess (11). 5. thermoforming device according to claim 4, characterized in that a plurality of extensions (14) are provided. 6. Thermoforming device according to claim 5, characterized in that the extensions (14) are arranged distributed uniformly around the central axis (13). 7. Thermoforming device according to one of claims 4 to 6, characterized in that the extensions (14) have an approximately semicircular cross-section in plan view with rounded outlet areas (15).

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