X-ray or gamma ray systems or devices – Beam control – Window
Reexamination Certificate
1999-08-23
2001-10-09
Porta, David P. (Department: 2876)
X-ray or gamma ray systems or devices
Beam control
Window
C356S244000
Reexamination Certificate
active
06301335
ABSTRACT:
The present invention relates to an analyzer measuring window and to a method for installing said measuring window in place, said measuring window being used in essentially automatic and continuously operated measurements, particularly when analyzing the element contents of solid, liquid or slurry-like materials.
In continuously operated element content measurements, the applied method of analysis is usually the X-ray fluorescence method, where the samples to be analyzed generate, by means of the radiation quantums emitted from the X-ray source, radiation that is characteristic of each element. The intensity of said characteristic radiation is dependent on the element content in the sample, and therefore the radiation intensity is measured by means of a detector which, together with the X-ray source, is installed at the measuring head of the analyzer. In an online analysis, the measuring head is protected by sealing in order to eliminate the effects of surrounding dust and possible changes in the liquid temperature. Particularly when analyzing liquid or slurry-like materials, the sample to be analyzed is located in a specific chamber, and the measuring head is placed in a specific measuring chamber. In order to maintain the connection between the sample chamber and the measuring chamber, the wall of the sample chamber is provided with a sample aperture, and the wall of the measuring chamber is provided with a measuring aperture, and said apertures are mutually positioned so that the measuring chamber and the sample chamber form an essentially closed space. In order to prevent the sample from entering the measuring chamber, and on the other hand from flowing out of the sample chamber, the measuring head provided in the measuring chamber is connected to the sample material contained in the sample chamber by intermediation of a measuring window that permeates X-ray radiation, and said measuring window is installed in between the measuring aperture and the sample aperture.
Generally the measuring window permeating X-ray radiation is made of a thin plastic material, which is tightened to form part of the analyzer wall. The measuring window must be compactly sealed and endure the pressure possibly prevailing in the measuring chamber. The geometric position of the measuring window in relation to the measuring head must essentially remain the same throughout the process, in order to achieve sufficient accuracy in the measurement of the radiation intensities. Thus the measuring window must not be essentially bulged or ballooned, for instance owing to the pressure possibly prevailing in the measuring chamber.
In continuously operated measurements, the measuring window wears for instance when the sample flows past the measuring window, or when solids are precipitated on the window surface, in which case there is an error in the analysis results owing to the measuring window. Therefore the measuring window must be replaced from time to time. If the measuring window is not replaced, it wears until it breaks, or then the degree of errors in the analysis results essentially weaken the measuring accuracy. Usually measuring windows are disposable, and they are replaced manually when necessary. In practice, the replacing of measuring windows is the most important and often the most frequent maintenance operation required by analyzers, which in part increases the analyzer operation and maintenance costs.
The above described process of replacing measuring windows is simplified in the U.S. Pat. No. 5,050,201, where the measuring head of a device applying X-ray fluorescence is protected by means of a film that is movable with respect to the sample. The film is arranged to rest on two spools, so that when necessary, the film can be advanced in order to obtain a new, clean film surface in front of the measuring head. According to the U.S. Pat. No. 5,050,201, the film is kept in place, in readiness for operation, only by means of the friction between the film and the supporting spools. Thus the film is easily advanced when necessary, but on the other hand a film installed in this fashion does neither separate the sample tightly from the measuring head nor prevent the sample from flowing out of the sample chamber, and it certainly does not provide any protective sealing for the measuring head. Moreover, the film according to the U.S. Pat. No. 5,050,201 does not endure any pressure directed to the measuring head or surrounding it. Consequently the measuring accuracy of the device is weakened, because the position of the film in relation to the measuring head is subjected to alterations.
The object of the present invention is to eliminate some of the drawbacks of the prior art and to achieve an improved analyzer measuring window, which is more reliable in operation and is suited for solid, liquid or slurry-like materials, as well as a method for installing said measuring window in place; said measuring window can be replaced at least between two measuring periods without manual operation, and the position of the window in relation to the measuring head can be maintained essentially permanent throughout the whole measuring period. The essential novel features of the invention are apparent from the appended claims.
The analyzer measuring window according to the invention is advantageously used in an online-type analysis of element contents where X-ray fluorescence is applied, and where the sample to be analyzed is advantageously contained in a specific sample chamber and the measuring head is located in a specific measuring chamber. In order to maintain the connection between the sample chamber and the measuring chamber, the wall of the sample chamber is provided with a sample aperture, and the wall of the measuring chamber is provided with a measuring aperture, and said apertures are mutually positioned so that the measuring chamber and the sample chamber form an essentially closed space. In order to prevent the sample from entering the measuring chamber, particularly when treating liquid or slurry-like materials, and on the other hand from flowing out of the sample chamber, the measuring head located in the measuring chamber is connected to the sample material contained in the sample chamber by intermediation of a measuring window permeating X-ray radiation, and said measuring window is installed in between the measuring aperture and the sample aperture.
According to the invention, the analyzer measuring window is formed of a ribbon made of elastic measuring window material, and said ribbon is movable in relation to the analyzer measuring head and can be installed in an essentially compact fashion against the wall of the measuring chamber containing the measuring head and against the wall of the sample chamber containing the material to be analyzed. The ribbon constituting the analyzer measuring window is advanced, during the measuring window replacing period between two measuring periods, essentially for an equal length. Moreover, because the ribbon constituting the analyzer measuring window can be installed in an essentially compact fashion with respect to the walls of the measuring chamber and the sample chamber, the measuring window advantageously remains, throughout the whole measuring period, essentially in place in relation to the measuring head. Thus the measuring accuracy of the analyzer also remains essentially the same throughout the measuring period. In addition, the measuring window is stretched tight with respect to the walls of the measuring chamber and the sample chamber, so that the measuring window is made to endure the pressure directed to the measuring window by the measuring chamber, in which case the bulging of the window surface during the measuring period is prevented by said measuring window.
In order to install the analyzer measuring window according to the invention in place in an essentially compact fashion with respect to the walls of the measuring chamber and the sample chamber, and at the same time in the desired position in relation to the measuring head, any sample possi
Alfthan Christian von
Mann Kari
Outokumpu Oyj
Porta David P.
Smith-Hill and Bedell
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