Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1999-08-02
2001-11-13
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S052000, C073S040700, C324S536000, C356S313000
Reexamination Certificate
active
06314796
ABSTRACT:
The invention relates to a process for non-destructively testing fluid-filled containers for leaktightness. Furthermore, the invention relates to a corresponding apparatus for non-destructively testing fluid-filled containers for leaktightness.
It is necessary to test the leaktightness of fluid-filled containers in many fields of technology, for example in the field of pharmacology. In this case, the container can be the cartridge of an item of pharmacological packaging, especially a cartridge for a propellant-free dosage aerosol.
Such cartridges have hitherto evaded an economic test for leaktightness.
Such a container for propellant-free application of a dosed quantity of a liquid medicament as a spray for inhalative application is described in international patent application WO 91/14468. The medicament solution is located in an exchangeable container which has a rigid outer container and a flexible inner container. An exactly-dosed quantity of the active ingredient solution is transferred from this container into a pumping chamber, and is there sprayed at high pressure through a small jet, wherein the particles which are formed are inhaled by the patient. Suitable containers are, for example, described in European patent document 532873. The advantage of this double-walled container is that the medicament solution can be removed without air or gas bubbles entering the inner container. Pressure compensation takes place by the inner flexible container collapsing upon itself whilst the rigid outer container provides protection from mechanical damage. The outer container contains openings for pressure compensation. If larger quantities of air or gas residue was to collect in the inner container, exact and reproducible individual dosage would no longer be guaranteed in the case of each individual application. A leak in the inner container, the walls of which comprise a very thin extruded foil, would result in gas and air bubbles forming during use, and possibly leading to a lower quantity of active ingredient solution being inhaled. In order to attain the greatest possible safety, it is thus necessary to test the container which is filled with the highly-effective medicament solution as to whether there is a leak in the inner container.
An economic test for leaktightness has hitherto not been found for this type of cartridge.
In order to detect traces of volatile materials, principally highly-sensitive sensors such as e.g. the flame ionisation detector or the photo ionisation detector are used in a known manner. However, these sensors are dependent on a gas atmosphere of at least atmospheric pressure; direct measurement in a vacuum is thus not possible. However, in order to be able to test the leaktightness of a container filled with a fluid, it must be brought into a vacuum so that a sufficient quantity of volatile material will be available for detection in the case of a leak. Furthermore, it is not possible to detect water traces in a gas atmosphere at a pressure below that of atmospheric pressure with any hitherto-known sensor.
It is also known, in gas analysis technology, to test the gas to be analysed emission-spectometrically, wherein the gas to be analysed is ionised by means of a constant high frequency discharge, in an evacuated gas discharge room, the pressure of which is between 0.01 and 5 Torr, i.e. a plasma is created wherein the light given off is spectrally decomposed and the intensities of the spectral lines which are characteristic of the ionised gases are photo-electrically measured (German patent specification 1 124 734). Similar processes and devices for gas analysis are shown in the document by Koch et al., “Über ein neuen Verfahren zur spektralen Gasanalyse”, in Angewandte Chemie, 71, 1959, pages 545-549; GB 2 185 573 A; DE 195 05 104 A1; German patent document 1 087 832; U.S. Pat. No. 3,024,745 and DE-OS 1 598 303.
However, these known processes and devices are based on the analysis of supplied analysis gas through a spectral analysis, and not on the test for leaktightness of containers filled with fluid.
The objective of the invention is to specify a process and an apparatus for non-destructively testing fluid-filled containers for leaktightness, which allows a leak to be detected with greater precision and in a simple manner.
The solution of this objective takes place according to the invention for the process with the following steps:
provision of the containers filled with fluid in a vacuum,
undertaking of a gas discharge in the vacuum,
recording of the light emissions emanating from the gas discharge, and
evaluation of the light emissions for changes caused by volatile container contents exiting the tested containers as a result of a leakage.
With regard to the apparatus, the solution of the objective, according to the invention, succeeds with:
a receptacle in which a pressure beneath that of atmospheric pressure can be maintained and in which the containers which are to be examined are kept,
a gas discharge space in a vessel connected to the receptacle and electrical apparatus for effecting the gas discharge,
a light-sensitive sensor arrangement for recording the light emitted by the gas discharge, and
an evaluation circuit for evaluating the emitted light for changes caused by volatile container contents exiting the tested containers as a result of a leakage.
If there is a leakage in the containers, a small quantity of the container contents evaporates due to the vacuum, wherein the gas discharge undertaken between two electrodes detects both a change in brightness and a change in the spectral composition of the light emitted by the gas discharge as a result of these traces of material. Indeed, this effect does remind one of the known methods of atomic spectrometry, where the light emission of elements driven from a plasma at high power and at atmospheric pressure are used for detection of these elements; however, the detection of compounds, especially of organic compounds, is not possible in a vacuum with this method of atomic spectrometry. In addition to this, the testing of containers filled with fluid at atmospheric pressure for leaktightness is practically not possible.
For example, the methodology of atomic spectrometry is described in:
Hoffmann, H. J., Röhl, R: “Plasma-Emissions-Spectrometrie”.
Analytiker Taschenbuch Vol. 5, pages 69-92, Springer-Verlag (1985), and
Brockaert, J. A. C., Schickling, C., Bings, N: “Mikrowellenplasmen für die Atomspektrometrie—Entwicklungsstand und analytische Anwendungen”. GIT Fachz. Lab. 4/96, pages 323-37.
The influence of the volatile container contents on the light emission of the gas discharge is especially clear when, according to an embodiment of the invention, the provision of the containers and the activation of the gas discharge takes place at a pressure of between 0.05 and 50 mbar, preferably at a pressure of between 1 and 4 mbar.
Furthermore, according to a further feature of the invention, it is necessary for the leaktightness test for the gas discharge to be carried out by high-tension electrical energy which is supplied capacitively or inductively or by means of electrodes.
Especially good results can be attained if the gas discharge is activated at high voltage, which can be a DC or AC voltage with a frequency of greater than 50 Hz, preferably from 30-40 kHz.
Evaluation of the light emission can be made according to various viewpoints. One way, according to a further embodiment of the invention, is that the reduction of the brightness of the light emitted by the gas discharge compared to the basic brightness with the mere presence of the residual gas molecules of air in a vacuum is recorded, and this change in brightness is evaluated in connection with a corresponding empirically-determined calibration curve with regard to the concentration of the respective volatile container contents.
Another way, according to an embodiment of the invention, is that the change in the wavelength of the light emitted from the gas discharge is determined and analysed with regard to the type of the volatile conta
Kuehnel Andreas
Poss Gerhard
Wittekind Juergen
Boehringer Ingelheim Pharma KG
Devlin M-E. M.
Raymond R. P.
Wiggins David J.
Williams Hezron
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