Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
2001-01-25
2002-12-17
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S041000, C073S045400
Reexamination Certificate
active
06494083
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for testing the tightness and correct closure of a plurality of containers which are transported on a conveyor, the containers succeeding each other at brief time intervals, the containers being sealed by attaching a closure, and a characteristic of the containers which is dependent on the internal pressure (=internal-pressure characteristic) being measured at time intervals after the attachment of the closure.
BACKGROUND OF THE INVENTION
In the case of rigid containers such as glass bottles, the internal-pressure characteristic is typically the oscillation frequency of the closures, but in the case of flexible containers, such as PET bottles, it is the fill level.
Until now, the tightness of rigid containers, e.g. glass bottles which contain fruit juice or beer, has been tested by measuring the internal pressure. This test was carried out about 5 minutes after filling and closure. In the case of fruit juices which are poured in when hot, a negative pressure develops within this period due to cooling, whereas in the case of beer a slight positive pressure of 0.6 to 1.5 bar builds up due to the CO
2
which is released. In the case of fruit juices which are heated in a pasteurizer after closure, a higher pressure develops. It is known to ascertain this pressure by measuring the oscillation frequency of the container closure (DE-A-40 04 965 and DE-A-196 46 685). The measurements are encumbered with great uncertainty, as the measured frequency is evidently affected by other parameters, regarding which reference is made to the simultaneously filed international patent application “Method for Testing Sealed Containers” (=DE patent application 198 34 218.7).
The object of the invention is therefore, in the case of a method of the type described at the outset, to improve the reliability of the testing of the tightness or the closure.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved in that:
during the attachment of the closures to the containers
the internal-pressure characteristic is measured and/or
parameters of the closures or containers are recorded, knowledge of which is necessary to ascertain the internal pressure from the measurement of the internal-pressure characteristic;
the containers are marked, no later than when the closure is attached, in a way which permits the values which are measured or recorded upon attachment of the closures to be allocated to the respective container,
the internal pressure of the container is ascertained form the value of the internal-pressure characteristic measured at the time interval after the attachment of the closure
and comparison with the value of the internal-pressure characteristic measured upon attachment of the closure, or
taking into account the recorded parameters.
A criterion for the tightness or correctness of the closure is derived from the ascertained internal pressure value. Of course, the internal pressure need not be measured numerically. It is sufficient to ascertain a variable which is representative of the internal pressure, or else only to establish whether this variable lies above or below an empirically ascertained threshold value.
The fact that the internal-pressure characteristic of the containers is recorded when attaching the closures means that this recording takes place before the internal pressure rises or falls. If a parameter of the closures or containers is recorded, knowledge of which is necessary for the measurement of the internal-pressure characteristic, it is sufficient to record this parameter, as long as the respective container can be tracked and an allocation is therefore still possible.
The period between attaching the closures and measuring the internal-pressure characteristic can be so great that a large number of containers can be transported on the conveyer within this period.
In the case of drinks containing CO
2
, the measurement takes place e.g. after 10 minutes. In the case of fruit juices which are pasteurized, the internal-pressure characteristic can be measured after the pasteurizer.
With the process alternative, in which the internal-pressure characteristic is recorded when attaching the closures to the containers, this characteristic is measured twice, namely the first time when attaching the closures to the containers and the second time after the time interval mentioned. The first measurement then corresponds to the internal pressure zero, so that this value essentially depends only on the properties of the closure and/or cap (=closure parameters). The deviation of the value obtained during the second measurement from the value obtained during the first measurement is therefore almost exclusively attributable to the change in the internal pressure, so that the difference in the measured value shows, directly and in general even linearly, the increase or reduction in the internal pressure.
If, on the other hand, the properties of the closure and/or the cap (=closure parameters) are recorded when attaching the closures to the containers, the internal pressure is then ascertained during the later measurement of the internal-pressure characteristic from the measured value of this characteristic, by means of empirical values which are stored in value tables for the parameters. Each cap and/or additionally each closure type then has, so to speak, its own parameter set and threshold value for the measured frequency in the case of rigid containers or of the fill level in the case of plastic containers, with which the ascertained frequency or the ascertained fill level are compared. The influence of the properties of the closure blank or attached closure, e.g. material thickness and compound quantity), and of the properties of the closure chuck, e.g. the closure force, on the oscillation frequency of the attached closure is described in the simultaneously filed international patent application “Method for Testing Sealed Containers” (=DE patent application 198 34 218.7).
The marking of the containers makes possible a permanent allocation to the individual containers of the value of the characteristic recorded when attaching the closure or of the other parameters.
The measured values and the parameters can be attached direct to the container by means of the marking.
Another possibility consists of consecutively numbering the containers by means of the marking and then storing with each container number in a computer the internal-pressure characteristic measured during the attachment of the closure or the recorded closure parameters. The consecutive numbering can take place periodically as, by and large, the containers are moved along or emerge from the pasteurizer in turn. If the containers are already continuously or periodically numbered, this numbering can be used for the allocation of the recorded value or parameters to the containers.
In the case of rigid containers such as glass bottles, however, the marking preferably contains only information about the oscillation frequency of the closure as ascertained during the first measurement, the first measurement in general taking place directly after closure. As indicated, this oscillation frequency depends primarily on the type of closure and the closure force of the closure chuck (=closure parameters). At the second measurement, if e.g. a positive pressure has built up in a beer bottle sealed with a crown cap, a frequency deviating from this is measured, in most cases a higher frequency. The frequency increase is solely attributable to the positive pressure which has built up in the meantime. During the first measurement, carried out directly after the pressing on of the crown cap, the frequency is e.g. between 7 and 8 kHz, the differences between the individual bottles being caused by differences in the thickness of the crown cap material and the varying closure force of the closure chucks (closure parameter). After 5 minutes, a positive pressure e.g. of 1 bar has built up, which led to a frequency higher by 0.7 kHz b
Garber Charles D
Gardner Carton & Douglas
Heuft Systemtechnik GmbH
Williams Hezron
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