Measuring and testing – Gas analysis – With compensation detail
Patent
1992-08-31
1994-12-06
Williams, Hezron E.
Measuring and testing
Gas analysis
With compensation detail
73 3103, G01N 3344
Patent
active
053699750
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and a measuring arrangement for the automatic selection of containers, depending on whether the containers or possibly their contents are contaminated with an admissible or an inadmissible group of contaminations, as well as to a plant with such a measuring arrangement.
BACKGROUND
From the EP-A-0 306 307, which herewith is declared an integral part of the present description, it is known, within the framework of the recycling of containers, to detect on empty containers, in particular plastic containers, e.g. plastic bottles, whether any contaminations are present inside the container.
To this end it is proposed to detect such contaminations with the aid of an ionization technique, e.g. flame ionization or photo ionization in the UV-range, and if need be to eliminate the contaminated containers before re-filling them.
From the W088/00862 a selection method of containers is known, with which either distilled water is sprayed into the containers, water that may now be contaminated is removed from the containers and analysed, or water is sprayed into the containers, shaken in same and then analysed.
To increase the analysis redundancy, it is well known to use two different analysis techniques. The output signal of the detectors of the two analysis techniques is first of all compared with reference data, the comparison result is then compared with a correlation value range which depends on the specific analysis technique and a specific product which originally was present in the container.
On which basis the deciding correlation factors are determined according to this publication, is not indicated. Described is the use of detectors which specifically detect a given substance, e.g. a sugar analyser, and the providing of two such detectors that respond with a narrow band to a substance would make it possible to detect compound contaminations.
In principle, with regard to the technique described in the W088/00862, it must be regarded as disadvantageous that liquid samples must be taken from the containers in question, so that the test method based thereon is extremely slow. On the other hand, because of the slowness resulting from the use of a liquid, there is sufficient time to test the liquid sample for contaminations under conditions that are practically similar to those in the laboratory.
SUMMARY OF INVENTION
The present invention proceeds from a method as described in the abovementioned EP-A-0 306 307, according to which gas from the containers is analysed. Already because of the flow properties of gas, compared to those of a liquid, the latter method results in a considerable shortening of the process cycles compared to the method of W088/00862, which is particularly important for the selecting of containers that are fed to the line in quick succession.
Proceeding from such a gas analysis process, the present invention proceeds from the recognition of the problem that known analysis methods for gas analyses supply output signals that depend both on the contaminating substance that is being detected as well as on its concentration, i.e. on two variables. This causes ambiguity in the evaluation of such individually viewed signals. Often it is not possible to differentiate whether a detected output signal indicates a concentration .alpha. of the substance A or a concentration .eta. of the substance B. With a measuring operation tht is being considered, the concentration .alpha. of the substance A may provide the same result as the concentration .beta. of the substance B.
Under the aspect of reliability, it is the object of the present invention to solve this problem.
This is achieved with the method of the abovementioned type when one proceeds in accordance with the method of the invention, or with a suitable measuring arrangement in accordance with the invention.
In the method of the invention the gas analysis is carried out by means of n analysis techniques (54a,b . . . ) with n.gtoreq.2, each of which produces different output signal p
REFERENCES:
patent: 3266292 (1966-08-01), Bailey
patent: 3321954 (1967-05-01), Bailey
patent: 4818348 (1989-04-01), Stetter
Burtscher Heinz
Matter Ulrich
Mukrowsky Michael
Nunlist Rene
Lehmann Martin
Roskos Joseph W.
Williams Hezron E.
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