Radiant energy – Invisible radiant energy responsive electric signalling – Ultraviolet light responsive means
Reexamination Certificate
1998-06-05
2001-03-20
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Ultraviolet light responsive means
C250S308000, C250S358100, C250S374000
Reexamination Certificate
active
06204507
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an apparatus for checking weights per unit area during production of sheets of material by means of a source of radiation, which irradiates the sheet of material or the material being measured, and for detecting residual radiation on a side of the material being measured opposite to a radiation source using a gas-filled ionization detector.
Such apparatuses are used, for example, for continuously measuring the thickness of cold-rolled or hot-rolled metal sheets or foils and also for continuously measuring the thickness of paper sheets or the like. The measurement is made pointwise using a radiation source, such as an X-ray or nuclear radiation source of suitable intensity, type of radiation and energy, the intensity of the radiation, attenuated by the sheet of material or by the material being measured, is measured by an ionization chamber. For the case that a thickness profile is to be measured over a whole width of the sheet of material, the source of radiation and the ionization chamber can be fastened to a carrier, which then, embracing the sheet of material to be measured, is moved transversely over it. However, it is a disadvantage in this case that the thickness continues to be measured pointwise, which leads, particularly in the case of very rapidly moving sheets of material, as is usually the case with mill trains, to the fact that only a basically incomplete statement can be made concerning the thickness of the material over the width of the sheet. Admittedly, it is possible to interpolate the measured values over the whole width of the material arithmetically; however, such a procedure does not always provide the desired accuracy.
A similar result is achieved if a plurality of ionization chambers is disposed linearly next to one another and the radiation source is moved in a traversing framework relative to the ionization chambers and transversely to the direction of motion of the sheet of material to be measured. The use of a linear source of radiation and an ionization chamber, which can be moved relative to this source, is also known.
However, when material is moving quickly, control processes and, with that, adjustments of a manufacturing process can be realized only with difficulty. For these reasons, measuring devices were developed with which continuous measurements over the whole width of the material are possible.
Such an apparatus for measuring the thickness of flat profiles is known from DE 31 40 714 A1. In this case, above the flat profile to be measured, one or more punctiform sources of radiation are disposed, to which, in each case, a plurality of ionization chambers are disposed below the flat profile. Since the sources of radiation are constructed as point sources and the radiation is masked in a fan fashion, the ionization chambers, assigned in each case to a radiation source, are directed towards the radiation source. For this purpose, the ionization chambers are disposed in a collimator girder, which is provided with cylindrical collimator openings, which have axes aligned precisely with the source of radiation. However, it is not achieved with this arrangement that the radiation intensity, reaching each ionization chamber, is the same.
A similar apparatus is evident from DE 37 07 107 A1. In this case, the ionization chambers or the detectors, distributed over the surface of the material to be measured, are disposed in several rows. With this, an improvement in resolution can be achieved.
It is a common feature of all these apparatuses that either an expensive mechanical traversing system is required or a highly precise alignment of the ionization chambers or of the detectors must be assured in order to arrive at comparable measurement results. Moreover, when several ionization chambers are used, an appreciable technical effort is required in order to assure, as far as possible, the same parameters for all ionization chambers. Failing that, an expensive, constant compensation must be carried out, since gas fillings necessarily result in changes in the parameters.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an apparatus for checking the weights per unit area which avoids deficiencies of the state of the art and, in particular, provides detailed information about weight per unit area.
Briefly stated, the present invention provides a device for testing flat materials during production of material webs using a radiation source from which radiation passes through the material under investigation. Residual radiation on another side of the material is detected by a gas-filled ionization detector having a detector arrangement including a plurality of interconnected sections provided with collector electrodes and arranged inside a common housing. The sections can together be evacuated and filled with an ionizable gas. Each of the sections is allocated its own radiation inlet window. The radiation source allocated to the sections has a linear radiation distribution.
According to a feature of the invention, it is further provided that the collector electrodes are mounted on electrically conducting connecting pieces, which are embedded over insulators in a bottom of the detector arrangement.
The present invention further includes the sections being disposed next to one another and covering a whole width of the material that is to be measured.
According to a still further feature of the invention, there is further provided a feature in that a shape of a radiation entry window corresponds to a cross section of the sections of the detector arrangement. In an embodiment the radiation entry window and the sections are constructed circularly and are disposed next to one another. Alternatively, the radiation entry windows are constructed circularly and the associated sections are constructed angularly. Still another option is that all the sections are provided with a common strip-shaped radiation entry window.
Yet another feature of the present invention is that the radiation source consists of an isotope source. Furthermore, the radiation source optionally extends over all of the sections.
Another feature of the present invention provides a collimator assigned to the radiation source. In an embodiment, the collimator is disposed between the radiation source and the material that is to be measured.
Another feature of the present invention includes a collimator having openings with cross section of which is smaller than a cross section of the radiation entry windows. Optionally, walls of the openings diverge in the direction of the detector arrangement.
Yet a further feature of the present invention provides that the radiation source is disposed directly above the material that is to be measured.
The present invention further provides that collector electrodes are connected with current-voltage converters. Further provided by the present invention is that values of measurements, supplied by the current-voltage converter, are digitized and are supplied in parallel or serially to an interface of an evaluating software.
Another feature of the present invention includes a point-shaped source of radiation assigned to each of the sections. Furthermore, radiation sources are disposed at an equal distance from the sections. Optionally, a soft beta emitter is used as radiation source. Alternatively, an industrial radiating system is used as a radiation source.
The invention provides for measuring a transverse profile of sheets of material so that it is possible to adjust a production process directly. Since it is no longer necessary to move the source of radiation and the measurement chambers during the measuring process, the technical effort is reduced appreciable. Moreover, a small distance between the source of radiation and the measurement chambers permits the use of soft radiation. The common gas filling prevents sensitivity changes caused by the filling gas.
REFERENCES:
patent: 3160753 (1964-12-01), Varner
patent: 4720808 (1988-01-01), Repsch
patent: 5025154 (1991-06-01), Ritala
Feige Christian
Hildebrandt Steffen
Urban Franz-Josef
Gabor Otilia
Hannaher Constantine
Jordan and Hamburg LLP
Vacutec Messtechnik GmbH
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