GB1563665A - Device for non-contact gauging of thickness or weight per unit area of sheet and like materials - Google Patents

Description

(54) DEVICE FOR NON-CONTACT GAUGING OF THICKNESS OR WEIGHT PER UNIT AREA OF SHEET AND LIKE MATERIALS (71) We, UKRAINSKY NAUCHNO ISSLEDOVATELSKY INSTITUT TSELLJULOZNO-BUMAXHNOI PROMYSHLENNOSTI, a State Enterprise organised and existing under the laws of the Union of Soviet Socialist Republic (U.S.S.R.), of ulitsa Kutuzova, 18/7, Kiev, U.S.S.R., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly de scribed in and by the following statement: The present invention relates to an im provement in devices for non-contact gaug mg of thickness or weight per unit area of sheet or like materials using radioactive sources, and can be utilized for controlling the production of paper, textiles, films and like materials.

It is to be understood that the sheet materials mentioned herein include not only sheets such as those from various materials - both flexible and rigid, but also films, strips, as well as hollow articles, wherein the section of a wall being gauged can be considered as a section of a flat body such as a sheet.

The present applicants U.K. patent No.

1338157 describes and claims a device for non-contact gauging the thickness or weight per unit area of sheet material, said device comprising a radioactive source on one side of the material and emitting ionizing radia tion to pass in a forward direction through the material, a detector of radiation located on said one side of the material, magnetic means mounted between the source and the detector on said one side of the material.

The magnetic means are arranged such that its field, on interacting with the ionizing radiation particles from the source, deflects them back through the material onto the detector and disperses them according to their energy levels.

It is an object of the present invention to provide an improved device for non-contact gauging of the thickness or weight per unit area of sheet material.

According to the present invention there is provided a device for non-contact gauging of thickness or weight per unit area of sheet and like materials, comprising a charged particles radiation source, located on one side of the material and arranged to direct the particles radiation through the material a charged particles radiation detector located on the same side of the material, and a magnetic means including spaced poles located on the same side of the material as said radiation source and detector, said magnetic means serving for arcuately deflecting the charged particles by its magnetic field and diverting the particles back through the same material for a second time, towards the detector, said radiation source and detector being interposed between the poles of said magnetic means.

Such an arrangement of the device for non-contact gauging of thickness or weight per unit area of sheet and like materials according to the present invention makes it possible to bring the radiation source and detector as near to each other, as practicable which results in a shorter pathway of radiation particles in the air, decrease in the scattering of the radiation flux and the effect of fluctuations of the air parameters, while the magnetic field acting through the entire space over the source substantially increases that part of the radiation flux, which is deflected into the detector, thus increasing the accuracy of gauging.

Preferably the magnetic means is divided into two sections, one of which encompasses the radiation source, and the other the radiation detector.

Preferably further the magnetic means is constructed and mounted so that the distance between the source section poles may be varied, which makes it possible to adjust the intensity of the magnetic field in this area in accordance with the thickness of the material being gauged or the energy of the source.

To enable the zone of interaction of the magnetic field with charged particles to be increased over the entire pathway of their movement and to achieve therefore the most efficient use of the radiation source, the radiation detector and the detector section of the magnetic means may be extended in the direction of charged particles deflection and dispersion according to their energy level.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 schematically represents a device for non-contact gauging of thickness or weight per unit area of sheet and like materials, in accordance with a first embodiment of the present invention; Figure 2 represents the device of Figure 1 as viewed from the material being gauged; Figure 3 represents the device of Figure 1 as viewed in the direction of arrow A; Figure 4 represents the device of Figure 1 as viewed in the direction of arrow B; Figure 5 represented a device for noncontact gauging of thickness or weight per unit area of sheet and like materials, according to another embodiment of the present invention as viewed from the material being gauged, wherein the source of ionizing radiation is removed for clarity of represen tation;; Figure 6 is a vertical section take along line VI-VI of the device of Figure 5 and Figure 7 is a sectional view taken along line VII-VII of the device represented in Figure 6.

Referring to the drawings, and particularly to Figures 1, 2 the device for non-contact gauging of thickness or weight per unit area of sheet and like materials comprises a charged particle radiation source 1 enclosed in a protective chamber 2 having an aperture 3 and is situated on one side a material to be gauged. The function of the window 3 is to direct the radiation through the material 4. Said device also comprises a magnetic means 5 intended for arcuately deflecting the charged particles by its magnetic field and diverting them back through the same material 4 for the second time towards the detector 7. The magnetic means 5 may be either a permanent magnet or an electromagnet. A radiation detector 7 adapted to detect the radiation that has passed through the material 4 in the reverse direction is located on the same side of the material as the radiation source 1.The radiation detector 7 is an ionization chamber with a load resistor 8 connected to the input of an amplifier 9 whose output is connected directly to a recording device 10.

The radiation source 1 and the radiation detector 7 are interposed between the poles of the magnetic means 5.

In accordance with one of the embodiments of the present invention represented in Figures 5, 6 and 7, the magnetic means is divided into two sections, one of which having poles 6 encompasses the radiation detector 7 and the other having poles 11 encompasses the radiation source 1. The magnetic means 5 is constructed and mounted so, that the distance between the source section poles 11 can be varied, and thus the intensity of the magnetic field in the area of the radiation source 1 can be adjusted. With this aim in view the pole shoes 11 are mounted with the aid of screws 12 on blocks 13 adapted to slide in a slot 14.

The blocks 13 are moved with the aid of a two-way screw 15 passed through the respective right-and left-hand threaded holes in blocks 13. The screw 15 is checked against avial displacement by means of a strip 16 as is best seen in Figures 5 and 7. The radiation source 1 (Figure 7) is mounted on a support 17 which can be of any conventional suitable form. The size and strength of the magnetic means 5, the size and shape of the pole shoes 6 and 11, as well as the distance between the poles 11 are selected so that the magnetic field intensity, as well as the zone of interaction field intensity, as well as the zone of interaction thereof with the charged particles passing through the material 4 will be sufficient for arcuately deflecting the charged particles for a second time through the material in the direction to the radiation detector 7.

The radiation detector 7 and the pole section of the magnetic means which encompasses it are extended in the direction of charged particles deflection as is shown in Figures 1 and 2. This particular radiation detector 7 makes it possible to increase the zone of interaction of charged particles with the magnetic field, and thus utilize the activity of the radiation source with greater efficiency.

The magnetic field disperses charged particles according to their energy levels. In Figure 1 this is represented as several path ways of these particles corresponding to energy levels, El, E and E2, where E1 is the low energy level, E is the medium energy level and E2 is the high energy level.

The device also comprises power sources and other auxiliary units which are neither illustrated in the drawings nor described in detail since they are well known to those skilled in the art.

The principle of operation of the device for non-contact gauging of the thickness or weight per unit area of sheet and like materials is as follows: Charged particle flux from the radiation source 1 through the window 3 of the protective chamber 2 is directed onto the material 4 and while passing there through it is partially absorbed therein and comesinto the magnetic field produced by the magnetic means 5. In the magnetic field the particles of low energy deflect and move along more curved paths, whereas highenergy particles are deflected to a lesser degree and their path ways are less curved. Thus, the particles are dispersed in accordance with their energy levels and are deflected for a second passage through the material in the direction towards the radiation detector.The degree of absorption of radiation varies according to the thickness of the material being gauged, as does ionizing current in the radiation detector 7, and consequently, the voltage across the load resistor 8. This variation in voltage across the load resistor 8 is increased thrugh the amplifier 9 and recorded by the recording means 10 graduated either in thickness or weight per unit area units.

The device, according to the invention, due to the above-described arrangement of the radiation source and the radiation detector, makes it possible to bring them together as close as practicable. This arrangement increases the accuracy of gauging which results from the fact that the radiation particles on their way from the radiation source to the detector pass a shorter distance, and makes errors caused by changes in environmental parameters, such as air temperature, pressure, humidity, etc. decrease, whereas the efficiency of utilization of the activity of the radiation source increases due to the increased zone of interaction of the magnetic field with the particles along the entire pathway thereof, thus enabling both low-energy and high-energy radiation to be used.In the above-described device use can be made of a low-activity radiation source, small-size detector and magnetic means. This in turn simplifies radiation protection reduces the mass and size of the thickness gauge comprising a radiation source, radiation detector and magnetic means.

WHAT WE CLAIM IS: 1. A device for non-contact gauging of thickness or weight per unit area of sheet and like materials, comprising a charged particles radiation source, located on one side of the material and arranged to direct the particles radiation through the material a charged particles radiation detector located on the same side of the material, and a magnetic means including spaced poles located on the same side of the material as said radiation source and detector, said magnetic means serving for arcuately deflecting the charged particles by its magnetic field and diverting the particles back through the same material for a second time, towards the detector, said radiation source and detector being interposed between the poles of said magnetic means.

2. A device as claimed in Claim 1, wherein the magnetic means is divided into two sections, one of which encompasses the radiation source, and the other the radiation detector.

3. A device as claimed in Claim 2, wherein the magnetic means is constructed and mounted so that the distance between the source section poles may be varied.

4. A device as claimed in Claim 2, wherein the radiation detector and the detector section of the magnetic means are extended in the direction of charged particles deflection and dispersion according to their energy levels.

5. A device substantially as herein described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. materials is as follows: Charged particle flux from the radiation source 1 through the window 3 of the protective chamber 2 is directed onto the material 4 and while passing there through it is partially absorbed therein and comesinto the magnetic field produced by the magnetic means 5. In the magnetic field the particles of low energy deflect and move along more curved paths, whereas highenergy particles are deflected to a lesser degree and their path ways are less curved. Thus, the particles are dispersed in accordance with their energy levels and are deflected for a second passage through the material in the direction towards the radiation detector.The degree of absorption of radiation varies according to the thickness of the material being gauged, as does ionizing current in the radiation detector 7, and consequently, the voltage across the load resistor 8. This variation in voltage across the load resistor 8 is increased thrugh the amplifier 9 and recorded by the recording means 10 graduated either in thickness or weight per unit area units. The device, according to the invention, due to the above-described arrangement of the radiation source and the radiation detector, makes it possible to bring them together as close as practicable. This arrangement increases the accuracy of gauging which results from the fact that the radiation particles on their way from the radiation source to the detector pass a shorter distance, and makes errors caused by changes in environmental parameters, such as air temperature, pressure, humidity, etc. decrease, whereas the efficiency of utilization of the activity of the radiation source increases due to the increased zone of interaction of the magnetic field with the particles along the entire pathway thereof, thus enabling both low-energy and high-energy radiation to be used.In the above-described device use can be made of a low-activity radiation source, small-size detector and magnetic means. This in turn simplifies radiation protection reduces the mass and size of the thickness gauge comprising a radiation source, radiation detector and magnetic means. WHAT WE CLAIM IS:

1. A device for non-contact gauging of thickness or weight per unit area of sheet and like materials, comprising a charged particles radiation source, located on one side of the material and arranged to direct the particles radiation through the material a charged particles radiation detector located on the same side of the material, and a magnetic means including spaced poles located on the same side of the material as said radiation source and detector, said magnetic means serving for arcuately deflecting the charged particles by its magnetic field and diverting the particles back through the same material for a second time, towards the detector, said radiation source and detector being interposed between the poles of said magnetic means.

2. A device as claimed in Claim 1, wherein the magnetic means is divided into two sections, one of which encompasses the radiation source, and the other the radiation detector.

3. A device as claimed in Claim 2, wherein the magnetic means is constructed and mounted so that the distance between the source section poles may be varied.

4. A device as claimed in Claim 2, wherein the radiation detector and the detector section of the magnetic means are extended in the direction of charged particles deflection and dispersion according to their energy levels.

5. A device substantially as herein described with reference to and as illustrated in the accompanying drawings.