EP0430195A1 - Rotary closure made by deep-drawing of aluminium for glass-bottles under internal pressure and deep-drawing device for a closing-head to make such rotary closures - Google Patents

Abstract

A threaded closure made by deep-drawing of aluminium for glass bottles under internal pressure, wherein the tightness after filling is to be determined via deformation changes on its upper closure surface 4, has a particular shape at its upper closure surface 4 for the purposes of greater deformation changes which can thus be registered more reliably. Directly after completion of the closure operation, the upper closure surface 4 is thus pressed a short way with its central region 7 into the interior of the glass bottle and can be deformed in such a way that the central region 7 can be pressed outwards under the subsequent effect of sufficient internal pressure. Such threaded closures are also particularly suitable for fully automatic control measurements. In the deep-drawing device, also specified, for a closing-head to make such threaded closures, a stop 13, held displaceably in the inner cutout 12 of a die 8, is to have a central pressing-on surface 15 which extends a short way beyond the base area 16 of the stop 13 and is arranged concentrically to the mid-axis 9 of the die 8. <IMAGE>

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, wherein a sealing compound is arranged on the inside of the end surface, in particular close to the transition to the threaded surface, by means of which the deformed 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 on the 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 serves to deep-draw the blank down to the side mouth of a glass bottle, and in which Third recess, a stop (abutment) is slidably held, which can be pressed against the force of a compression spring into the interior of the die.

State of the art

There are deep-drawn screw caps in which the upper end surface is always up bulges. While the curvature is generally only slight after the closing process has ended, it subsequently increases under the influence of the internal pressure. However, this only applies to intact glass bottles with perfect screw caps, because only then can an effective internal pressure build up. Thus, the specified change in deformation can in principle be an indicator of the proper condition and filling of the glass bottle or, in other words, its tightness.

It is therefore also common practice to measure the change in deformation for control purposes. Such control measurements, however, encounter various difficulties. So the deformation of the twist locks. i.e. the upper end surface of the mouth of the glass bottle, of course. There are practically no longer any differences measurable.

Rather, only the middle area of the upper end surface is suitable for a measurement. However, there are sometimes no sufficiently clear differences. Finally, only gradual changes in the (outward) curvature are considered for changes in deformation, which understandably is not always sufficient as a basis for reliable detection, even with narrow manufacturing or closing tolerances.

It can happen that glass bottles are considered to be depressurized due to the curvature of the upper end surface of their screw caps, but are actually under internal pressure and vice versa. In other words, the previous control measurements must be carried out with great precision and a correspondingly high level of effort, but nevertheless do not always deliver reliable results.

The above restrictions relate to twist-off closures of relatively large diameter, as are known in practice as so-called twist-off closures. For twist locks with smaller diameters, i.e. less than 35 mm, the deformation changes are even so limited that they are ruled out for practical measurements and are therefore not made. Such glass bottles nowadays leave the filling stations in large quantities (annually 10 billion pieces annually in the FRG and 30 billion pieces throughout Europe). Their tightness is simply assumed, or the glass bottles are only checked for leaks on a random basis (e.g. 1 - 2 bottles per 100,000 pieces or hour), the twist-off caps being pierced and gas samples taken. The twist locks are inevitably damaged or destroyed. In view of an estimated error rate of 1 bottle per 10,000 pieces, such a tightness check is extremely random and unsatisfactory, especially where it is associated with the destruction of the screw caps.

Presentation of the invention

This is where the invention begins. She would like to propose a twist lock of the type specified, which can be checked easily and without any doubt for tightness, even with diameters under 35 mm. This should reliably identify all possible errors that lead to leakage (such as missing or damaged seals, damage to the bottle mouth before or during filling, closing, pasteurizing if necessary, etc.). In particular, a possibility for the rapid detection and sorting out of leaky bottles is also to be created, which can keep pace with the current filling capacities and ultimately up to 100,000 bottles per hour can run fully automatically and non-destructively. As a result, comprehensive and permanent quality control should be made possible without reducing productivity.

This object is achieved with a screw cap of the type specified according to the invention in that the upper end surface immediately after the closure process is pressed with its central region somewhat into the interior (below the upper mouth edge) of the glass bottle and is deformable in such a way that the central region is below the the subsequent action of sufficient internal pressure (above the upper edge of the mouth).

Unlike before, the initial state of a glass bottle under internal pressure should be such that the upper end surface, i.e. its central area is not already curved or convex, rather a curvature directed into the interior of the glass bottle is initially provided. This type of deformation allows a larger and thus also easier and more reliable measurement of the change in the upper end surface when the internal pressure builds up. The curvature normally regresses, so to speak, in the direction of a zero position (at the level of the upper edge of the mouth), in order to then appear more strongly above this zero position.

Compared to the previous measurement technology (for screw caps with a relatively large diameter), this means that not only gradual differences of a rectified deformation have to be detected, but a reversal of direction in the deformation as an additional recognition feature with more mobility, which makes control easier and also makes it safer.

For twist locks with a smaller diameter, ie less than 35 mm, as is the case for numerous carbonated bottles term beverage bottles, and in particular mineral water or lemonade bottles, is customary, the proposal of the invention means that this is the first time that detection and sorting out of leaky bottles has become possible due to measurable changes in deformation. The changes can be detected so reliably and quickly that fully automatic control measurements can be carried out in the filling or closing cycle.

The proposed screw cap can be produced from a blank during the closing process by deforming the same, expediently in such a way that after placing a blank on the bottle mouth, the upper end face is first pressed into the inside of the bottle and then the blank is deep-drawn and the thread rolled. This creates levels of deformation without abrupt or abrupt transitions and also gives the upper end surface sufficient mobility.

In contrast, the invention cannot be implemented with preforms which have already been correspondingly deformed. Permanent pre-deformation can generally only be achieved through special deformation measures, such as beads or the like. This, in turn, would inevitably limit later mobility, which is required for control measurements.

Otherwise, pre-deformation causes difficulties for the introduction of the sealing compound, in particular the insertion of a (flat) sealing washer and the like. Another difficulty is centering. This is not guaranteed in the case of pre-deformation, ie the deepest vertex would not necessarily reach the center of the mouth where the control measurement is to take place later.

The upper end surface with its central area should be pressed into the interior of the glass bottle at least 0.4 mm (below the upper mouth edge) after the closing process and should be deformable by a similar amount in the opposite direction.

This applies in particular to screw caps with a diameter in the range of 30 - 35 mm. The depth of impression to be selected also depends on the material thickness and the internal pressure to be expected. It is also important with what speed and accuracy should be measured, so that the production speed is also an influencing factor.

The upper end surface with its central region is advantageously pressed into the interior of the glass bottle about 0.7 mm (below the upper mouth rim) and deformable in the opposite direction by a similar amount.

For a deep-drawing device of the type mentioned at the outset, the invention proposes that the stop has a central pressing surface which protrudes somewhat beyond the base of the stop and is arranged concentrically with the central axis of the die. The middle pressure surface can - like the rest of the base. - be essentially flat. In particular, it can have the shape of a truncated cone.

The middle pressing surface should be at least 0.4 mm emerge from the base of the stop. - The central pressure surface advantageously emerges about 0.7 mm above the base surface of the stop.

According to a further proposal, the ratio of the diameter of the middle contact surface to the entire base area of the stop is at least 1: 2. This means that not only a partial deformation but also a flat deformation takes place.

Brief description of the drawing

Fig. 1

einen erfindungsgemäßen Drehverschluß an einer Flaschenmündung unmittelbar nach Beendigung des Verschließvorganges im Schnitt,

Fig. 2

den Gegenstand von fig. 1 zu späterem Zeitpunkt unter Einwirkung eines Innendrucks in dichtem Zustand (ausgezogene Linien) bzw. bei späterem Druckabfall (gestrichelte Linien) und

Fig. 3

den unteren Teil einer erfindungsgemäßen Tiefziehvorrichtung im Schnitt über der Mündung einer Glasflasche, wobei die rechte Hälfte den Zustand vor Beginn und die linke Hälfte den Zustand nach Beendigung der Verformung der oberen Abschlußfläche eines Drehverschlusses wiedergibt.

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

Fig. 1

a twist lock according to the invention on a bottle mouth immediately after completion of the closing process in section,

Fig. 2

the subject of fig. 1 at a later point in time under the influence of an internal pressure in a sealed state (solid lines) or in the event of a later pressure drop (dashed lines) and

Fig. 3

the lower part of a deep-drawing device according to the invention in section over the mouth of a glass bottle, the right half showing the state before the start and the left half the state after the deformation of the upper end face of a screw cap.

1 and 2 is on the mouth of a glass bottle with an upper mouth 1 and a side mouth 2 and an external thread 3, a deep-drawn rotary closure made of aluminum with an upper end face 4, a lateral thread surface 5, not a Darge here provided circlip and a sealing compound 6. After completion of the closing process, in which a blank together with the sealing compound 6 is deep-drawn onto the lateral mouth edge 2 and the lateral thread surface 5 is formed by rolling, the upper end face 4 of the screw cap, more precisely, is the middle area 7 slightly pressed into the inside of the glass bottle, i.e. below its upper rim 1. As a rule, this is an unstable state, which only exists and should exist initially.

As soon as a stronger internal pressure takes effect when the glass bottle is closed, as is regularly to be expected in the event of a certain idle time due to the release of gases and especially when heated, the upper end surface 4, i.e. raise the central region 7 above the plane of the upper mouth edge 1, which could be called a kind of zero position, and deform it in the opposite direction, as shown by solid lines in FIG. 2. This change in deformation is almost visually recognizable, but in any case it can be measured easily and reliably by measurement. However, this condition can only be achieved with intact glass bottles and tight closures or sufficient gas addition, which is why it can be described as correct. It should absolutely be reached and continue until the products are used up.

If, on the other hand, the glass bottle including the screw cap is defective or if there is a leak later, the shape described above, ie the outward curvature of the central region 7 of the upper end face 4, can also occur again regress. If the pressure loss becomes effective immediately after the filling or closing and possibly pasteurizing process, i.e. at the manufacturer, a complete reset and thus reliable detection can be expected. If, on the other hand, the leakage occurs later (at the dealer, consumer), a partial provision up to approximately zero position is to be expected, as is indicated by dashed lines.

Fig. 3 illustrates the basic structure of a deep drawing device according to the invention for a closing head for producing the aforementioned twist locks. Thereafter, a die 8 has three recesses 10, 11, 12 concentric with a central axis 9. The first recess 10 tapers continuously from the outside inwards to approximately the largest outside diameter of the twist lock. This is followed by the second recess 11 with a constant diameter. This is followed by the third recess 12 with a smaller diameter, which is used to deep-draw the blank down to the lateral mouth edge 2. In the third recess 12 a stop 13 is slidably held, i.e. it can be pressed against the force of a compression spring 14 into the interior of the die 8, as shown with the left half of FIG. 3. This state is reached after the deep drawing. The stop 13 is then pressed in relative to its starting position shown with the right half by the amount of the intended drawing depth (for example 2.6 mm).

Before or when this end position is reached, the upper end face 4, namely with its central region 7, is additionally deformed, namely somewhat pressed into the inside of the glass bottle. This is ensured by a central pressing surface 15, which protrudes somewhat beyond the base surface 16 of the stop 14. For the rest, the central pressing surface 15 is arranged concentrically around the central axis 9 and here approximately frustoconical; their diameter is in relation to the diameter of the base area 16 in a ratio of at least 1: 2 and thus allows large-area deformation.

(Shaped) twist locks manufactured in this way can be easily and safely checked for leaks or leaks. The deformation changes that are considered for this are particularly suitable for a fully automatic inspection of the filled bottles.

Claims (7)

Deep-drawn aluminum screw cap for glass bottles under internal pressure with an upper end surface, a side threaded surface and, if necessary, a locking ring, whereby a sealing compound is arranged on the inside of the end surface, especially close to the transition to the threaded surface, by means of which a seal is used when the closure is deformed tion along the mouth edge of a glass bottle, characterized in that the upper end surface (4) immediately after completion of the closing process with its central region (7) is pressed somewhat inside (below the upper mouth edge (1)) of the glass bottle and is deformable in this way, that the middle area (7) can be pressed outwards under the subsequent action of sufficient internal pressure (above the upper rim of the mouth (1)). Screw cap according to claim 1, characterized in that the upper end surface (4) with its central region (7) is pressed into the interior of the glass bottle at least 0.4 mm (below the upper mouth edge (1)) after the closing process and by a similar amount is deformable in the reverse direction. Rotary closure according to claim 1 or 2, characterized in that the upper end surface (4) with its central region (7) is pressed into the interior of the glass bottle by about 0.7 mm (below the upper mouth edge (1)) and in by one similar dimension is deformable in the reverse direction. Deep-drawing device for a closing 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 continuously extending from the outside in to approximately the largest outer diameter of the twist lock is tapered connects second recess with a constant diameter and then finally follows a third recess with a smaller diameter, which is used to deep-draw the blank down to the side mouth of a glass bottle, and wherein in the third recess a stop is slidably held against the force a compression spring can be pressed into the interior of the die, characterized in that the stop (13) has a central pressure surface (15) which protrudes somewhat beyond the base (16) of the stop (13) and concentric to the central axis (9) of the die (8) is arranged. Deep drawing device according to claim 4, characterized in that the central pressing surface (15) protrudes at least 0.4 mm beyond the base surface (16) of the stop (13). Deep-drawing device according to claim 4 or 5, characterized in that the central pressing surface (15) protrudes about 0.7 mm above the base surface (16) of the stop (13). Deep-drawing device according to one of claims 4 to 6, characterized in that the ratio of the diameter of the central pressure surface (15) to the entire base surface (16) of the stop (13) is at least 1: 2.

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