Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
2000-02-15
2001-06-05
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S049200, C073S052000
Reexamination Certificate
active
06240769
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for testing features of containers which are sealed by a closure, mechanical vibrations being excited in the closure and the mechanical vibrations being analysed. These feature may be for example the central fit of the closure on the container opening, the tightness of the attachment of the closure to the container opening or the residual air volume in containers in which the liquid is foamed up prior to closure in order to expel the residual air or which are to be filled to the rim for process-related reasons.
It is known from DE-A-40 04 965 to test below-atmospheric pressure closures with a spring-return top, in particular below-atmospheric pressure screw-type caps, for the tightness of their attachment by creating mechanical vibrations in the top, processing and evaluating the vibrations as regards their frequency, duration, time integral of the amplitude and/or attenuation and ascertaining the level of the below-atmospheric pressure in the container from this. The below-atmospheric pressure can for example be produced by blowing steam into the remaining residual volume of the container or by pouring the drink in hot. In each case, the below-atmospheric pressure develops only after the steam has cooled or when the drink has assumed the ambient temperature. Similar methods for measuring the tightness of the closure are also known for containers, in which the contents are subjected to above-atmospheric pressure, in particular drinks bottles with carbonated drinks such as mineral waters or beer. This above-atmospheric pressure also builds up only gradually. Testing the tightness of container closures indirectly by testing the above-atmospheric pressure or below-atmospheric pressure in a container is thus possible only if the below-atmospheric pressure has formed through temperature equalization or a degree of above-atmospheric pressure has formed through escaping carbonic dioxide. Immediately after the closures have been fitted by a closer, it is therefore necessary to wait for a certain time before the tightness test can be carried out. The containers are transported further for approx 8 m on a conveyor at a speed of approximately 0.5 m/s to 1.5 m/s during this time; assuming that a noticeable rise or drop in pressure arises only after 5-10 seconds at the earliest (even later for hot pouring), testing via differences in pressure is possible, according to the sensitivity of the measurement apparatus only from 5 to 10 meters behind the closer. In particular, because not only is the rise/drop in pressure small, but in addition the leak is extremely small.
When filling foaming drinks, in particular beer, care must be paid to enclose as little air as possible in the bottle, as the taste of the beer is adversely effected by the atmospheric oxygen. There is no possibility of continuously measuring the level of the enclosed air volume. At present, the level of air volume can only be checked by random spot checks by opening the beer bottle.
BRIEF DESCRIPTION OF THE INVENTION
The object of the invention is to facilitate the easiest possible testing of features of containers with closures.
This object is achieved with a method of the type mentioned initially in that the analysis of the vibrations excited in the closure is carried out directly after the fitting of the closures, i.e. before a noticeable below-atmospheric pressure or above-atmospheric pressure has built up in the container.
Features such as the central fit of the closure, the quality of the crimping with crown cap closures or the tightness of the attachment of the closure in twist-off closures or the correct fit and closure for can tops can be tested by the method according to the invention, also with products or filling techniques which produce no vacuum or above-atmospheric pressure. Furthermore a continuous monitoring of the air volume enclosed in the container is made possible for foaming drinks.
In particular, the frequency, the decay time of the vibration (attenuation), the time integral of the vibration amplitude and/or the absolute intensity of the vibration are examined when analysing the mechanical vibrations of the closure.
The mechanical vibration in the closure can be excited by a short magnetic pulse produced by means of a magnetic coil or by a short ultra sound pulse or mechanical impact. The mechanical vibrations of the closure can be detected by a microphone, inductively or by similar means.
The method according to the invention is firstly explained in more detail in the following, insofar as it relates to the examination and testing of the correct fit of container closures. The preferred procedure for this examination is that the decay time oft-the vibration is determined and it is checked, whether the decay time lies outside a specific threshold value range, which is then interpreted as an indication of an incorrect fit of the container closure.
Another or additional test criterion is the time integral of the vibration intensity (amplitude), which is referred to in the following as “energy”.
Testing occurs each time directly after the container closure has been attached. The influence of a change in the internal pressure after the container has been sealed can thereby be largely eliminated, as such a change in the internal pressure arises only with a certain time delay.
The object of the invention is finally to guarantee that the containers are tightly sealed. The tightness is however ascertained not directly by determining the internal pressure, but by the fact that the most frequent cause of leaking container closures is ascertained, namely the incorrect fit of the closure.
It has been shown that container closures, in particular crown cap tops, which sit crookedly or non-centrally on the opening of a drinks bottle differ from closures with the correct fit as regards vibration behaviour. The measurement of the vibration frequency does not in general permit certain distinction, as the frequency of crooked closures can also lie in the range of centered closures. The decay time of the vibration and the energy of the vibration have on the other hand proved to be a much more reliable distinguishing criterion. Both values admittedly also depend to a certain degree on the internal pressure. Mainly, however, they depend on the correct attachment of the closure to the container. It is plausible that a crooked top, similarly to an asymmetrically stretched eardrum, cannot develop clean vibrations. In particular, if the top sits so crookedly on the bottle that there is an aperture on one side between the top and the rim of the opening, top vibrations decay very quickly. It has been shown that the method according to the invention has an approx. 10% better certainty of recognition than a method in which the tightness of a closure is ascertained by means of frequency analysis.
In the earlier German Patent Application “Verfahren zur Bestimmung von Parametern, e.g. Fullstand, Druck, Gaszusammensetzung in verschlossenen Behältern” [Method for determining the parameters, e.g. fill level, pressure, gas composition in sealed containers], official file no. 196 46 685.7 dated Nov. 12 1996 (=PCT/EP97/06298- WO 9821557), a method for determining parameters of closed containers is given in which primary mechanical vibrations are excited in a container wall and then the secondary vibrations excited by the primary mechanical vibrations of the container wall in the container, which take place within the space between closure and the liquid, are recorded and analysed, the sought-after parameters being ascertained from the established frequency of the secondary vibrations. There is a time lag between the primary vibrations and the secondary vibrations, which can be recorded separately by correspondingly staggered measurement windows. The vibration to be observed in the second measurement window is attributable to the development of a standing wave between the top and the surface of the liquid. In a bottle which is not sealed correctly, the development o
Garber C D
Gardner Carton & Douglas
Heuft Systemtechnik GmbH
Williams Hezron
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