METHOD AND DEVICE FOR MEASURING THE GAS CONTENT OF MATERIALS PACKAGED IN PLASTIC FILMS, GLASS OR OTHER LIGHT-PERMEABLE MATERIALS AND SENSITIVE TO A GAS TO BE MEASURED

Abstract

A method for the non-invasive measurement of the gas content of at least one gas selected from O.sub.2, CO.sub.2, amines, nitrogen oxides, sulfur compounds, in transparent packages made of plastic films, glass or other light-permeable materials, in which a sensor material sensitive to the gas content in the interior of the package is excited by excitation light incident thereon to emit a fluorescent or luminescent light, the emitted fluorescent or luminescent light is detected in a detection device interacting with the sensor, whereupon the packaged materials or produced materials are subjected to sorting, and optionally counting, as a function of the gas content determined by an evaluation unit coupled to the detection device, comprising the steps of:

a) optionally deep-drawing the package;

b) applying a sensor material to the inner side of a cover for the package, or to the inner side of the package, and optionally drying the sensor material;

c) introducing into the package the materials to be packaged;

d) gas-tightly closing the package by the cover while introducing a modified atmosphere of the gas to be measured;

e) placing the package on a conveying and sorting device;

f) exciting the sensor material by at least one excitation light source arranged at a defined distance from the package;

g) detecting, in a contactless manner, the intensity of the fluorescent or luminescent light emitted by the sensor material as a function of the gas content in the interior of the package, by a detection device arranged at a defined distance from the conveying device during conveying of the package to the sorting device;

h) electrically or electronically converting in the evaluation unit a measurement value detected in the detection device;

i) optionally applying a pressure to the package, and performing steps t) to h) again;

j) outputting a confirmation signal or a rejection signal by the evaluation unit; and

k) forwarding the package to further processing or disposal as a function of the gas content in the package calculated by the evaluation unit, and a device therefore. (FIG. 1)

Claims

1. A method for the non-invasive measurement of the gas content of at least one gas selected from O.sub.2, CO.sub.2, amines, nitrogen oxides, sulfur compounds, in transparent packages made of plastic films or other light-permeable materials, with the proviso that said materials are deformable under pressure, in which a sensor material sensitive to the gas content in the interior of the package is excited by excitation light incident thereon to emit a fluorescent or luminescent light, the emitted fluorescent or luminescent light is detected in a detection device interacting with the sensor, whereupon the packaged materials or produced materials are subjected to sorting, and optionally counting, as a function of the gas content determined by an evaluation unit coupled to the detection device, characterized in that the following steps are performed: a) optionally deep-drawing the package; b) applying a sensor material to the inner side of a cover for the package, or to the inner side of the package, and optionally drying the sensor material; c) introducing into the package the materials to be packaged; d) gas-tightly closing the package by the cover while introducing a modified atmosphere of the gas to be measured; e) placing the package on a conveying and sorting device; f) exciting the sensor material by at least one excitation light source arranged at a defined distance from the package; g) detecting, in a contactless manner, the intensity of the fluorescent or luminescent light emitted by the sensor material as a function of the gas content in the interior of the package, by a detection device arranged at a defined distance from the conveying device during conveying of the package to the sorting device; h) electrically or electronically converting in the evaluation unit a measurement value detected in the detection device; i) applying a pressure to the package; j) performing steps f) to h) again; k) outputting a confirmation signal or a rejection signal by the evaluation unit; and l) forwarding the package to further processing or disposal as a function of the gas content in the package calculated by the evaluation unit.

2. The method according to claim 1, wherein the sensor material is applied to the cover of the package by pad printing, screen printing, offset printing, gravure printing, brushing or sputtering, or labeling.

3. The method according to claim 1, wherein a sensor material reacting to O.sub.2, CO.sub.2, NH.sub.3, amines or NO.sub.2 is applied to the cover of the package.

4. The method according to claim 1, wherein the package is evacuated during closure.

5. The method according to claim 1, wherein the measurement of the gas content is performed by the serial excitation and detection of the fluorescent or luminescent light at constant time intervals of 20 ms to 80 ms, an particular 50 ms.

6. The method according to claim 1, wherein measurement values obtained in the evaluation unit are assigned to absolute concentration values, and that the confirmation signal or the rejection signal is triggered as a function of the determined gas content on a sorting device, in particular a sorting shunt.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In the following, the invention will be explained in more detail by way of an exemplary embodiment and a drawing. Therein,

[0037] FIG. 1 is a schematic illustration of a measurement system according to the invention; and

[0038] FIG. 2 is a diagram depicting the measurement results for the content of a gas to be examined in a sample.

DETAILED DESCRIPTION OF THE INVENTION

EXAMPLE 1

[0039] Oxygen Content in Packages Containing Sausage

[0040] A plastic film intended as a cover film for a sausage package, on its surface constituting an inner side after packaging of the sausage product, is coated by sputtering with at least one discreet small spot of a sensor material. To this end, sensor spots are applied to the inner side of the cover-forming film in a contactless manner using a clocked color sputterer (drop on demand). The spots are subjected to drying for two seconds in a hot-air stream while the cover film is forwarded to the packaging device, where food product, e.g. sausage, is introduced into the lower part of the package and a modified atmosphere of the gas to be measured, i.e. O.sub.2 in the present case, is subsequently introduced into the package and hot-sealed. A thus produced package in a first step, immediately upon packaging, is placed on a conveyor device and subjected to contactless measuring of the oxygen content in the interior of the package during conveyance. To this end, a light pulse is emitted every 50 ms from an excitation light source arranged at a distance from the package, which excitation light excites the sensor material provided in the interior of the package to give off fluorescent light as a function of the oxygen content present in the interior of the package. The fluorescent light is focused on a photodiode by a plurality of lenses or mirrors disposed on the same carrier as the excitation light sources. On the photodiode is generated an electric pulse, which, in an electronic system connected to the photodiode, is digitally processed into measurement data relating to the oxygen concentration in the interior of the package.

[0041] A device of this type is illustrated in FIG. 1. In the device, excitation light pulsed via the excitation light source 1 is allowed to impinge on the sensor 2 disposed in the interior of the schematically illustrated package 3, wherein fluorescent light emitted by the sensor 2 and schematically indicated by 4 impinges on the detection device 6 via a plurality of lenses or mirrors 5. In the detection device 6, the fluorescent light is converted into an electronic signal, which signal is evaluated in the evaluation unit 7 in terms of intensity, and an absolute concentration of the oxygen content to be measured the sample is calculated from the intensity of the signal by comparison with a reference value obtained during a calibration process.

[0042] The evaluation unit during the passage of a plurality of packages 3 below the measuring unit, emits a measuring signal each time a sensor 2 has been excited with excitation light 1 to emit fluorescent light. A schematic diagram of the measurement signals is illustrated in FIG. 2. Therein, the measurement value detected in the detection device is assigned to an absolute measurement value by the sensors introduced for the packages 3 having previously been calibrated by the feeding of different gas concentrations and measuring, and the measurement values having been assigned to the respective gas concentrations. In doing so, an oxygen concentration in normal air of about 20% O.sub.2 is set and a calibration between 0.1% O.sub.2 and 20% O.sub.2 is performed, since in the interior of the packages an O.sub.2 content of 0.2% is to be present. In the diagram obtained by such an evaluation unit, a noise is plotted between a phase of −20 and +13, indicating the range in which no sensor is provided, wherein a phase between 13 and 50 represents the range in which the oxygen content in the interior of the sample is too high and the samples are to be rejected, and values having phases of more than 50 are values corresponding to admissible oxygen concentrations in the interior of the packages, thus defining goods that are in good order. From FIG. 2, it is apparent that a sample had too high an oxygen content in the interior of the package, which was subsequently sorted out immediately by the device and discarded.

EXAMPLE 2

[0043] Oxygen Content in a Cleaning and Storing Solution. For Contact Lenses, which is Contained In A Package According to the Invention

[0044] A cover film for a glass container intended as a storage container for contact lenses, on its surface facing the cleaning and storing solution after filling and packaging of the contact lenses, is each coated with a discreet spot of a sensor material. The coating is performed by screen printing, and the formed sensor spots are subjected to drying in a hot-air stream prior to being applied to storage container for contact lenses, which contains the storing solution in addition to the contact lenses.

[0045] The storing solution in this case is saturated with the gas to be measured, namely oxygen jot the present case. It has a known oxygen content, and the measurement of the oxygen content is effected relative to the ambient oxygen content, wherein differences in the O.sub.2 contents between the interior of the container and the outer side of less than 5% are sufficient to confirm that a sample complies with the predefined criteria, i.e. the oxygen content in the interior of the storage container, in particular the dissolved oxygen content, does not exceed a given limit value of 5%.

[0046] Glass containers filled sealed and sealed in this manner are subsequently placed on a conveyor device, and each individual bottle subjected to contactless measuring as described in Example 1, the results are recorded. In doing so, the excitation light source emits the excitation light in a pulsed manner, at a pulse width of 40 ms, in order to safeguard that all of the samples are actually measured. The measuring method itself is identical with that of FIG. 1. A measurement diagram obtained in the test of Example 2 indicates whether the oxygen concentration in the cleaning and storing solution for contact lenses is too high or too low or within the desired range.

[0047] In order to receive absolute safety that the produced package is indeed gas-tight, the method can also be carried out in such a manner that immediately after packaging a first measurement is performed as described above, the sample is subsequently pressurized, and after this a second measurement is performed. If the seal of the package is not tight all around, oxygen will in any case be taken up into the interior of the package following the application of pressure, whereupon the second measured value will no longer correspond to the first measured value, thus making clear that the package is leaking, whereupon the product can be immediately sorted out.

[0048] It goes without saying that it is not absolutely necessary to calibrate the sensors, but that relative measurements alone will also yield the desired results on whether the content of a package does have gas a combination within an admissible range.

[0049] The same arrangement can, for instance, also be used for measuring the gas contents in medicinal articles, pharmaceuticals and electronic components.

EXAMPLE 3

[0050] Measurement of the Oxygen Content in the Argon-filled Interspace of Double-glazed Insulation Windows

[0051] In this case, the sensor material is glued or printed to the side of a glass pane facing the interspace between the glass panes and externally excited and read out, as described in Examples 1 or 2. This serves to check whether the filling level with noble gas is sufficiently high.