Radiation source shutter device and measuring device

Abstract

To obtain a radiation source shutter device that can ensure the wall thickness of a rotatably supported holding portion and downsize the device.SOLUTION: A radiation source shutter device 20 comprises: a storage body 21 inside which a storage space 21a is formed; a holding body 22 that is accommodated in the storage space 21a and in which a recess 22a is formed on an outer peripheral surface; a radiation source capsule 23 that is inserted into the recess 22a; and a bearing 24 that makes the storage body 21 rotatably support the holding body 22 around a rotation axis 2 extending so as not to overlap an entrance 22b of the recess 22a. A through-hole 21b that overlaps a portion of the trajectory of the entrance 22b of the recess 22a when the holding body 22 rotates is formed in the storage body 21. The bearing 24 does not overlap an inscribed circle 3 virtually inscribed in the storage body 21 when viewed from a direction perpendicular to the rotation axis 2; a portion of the inscribed circle 3 enters the inside of the bearing 24; and the inner diameter of the bearing 24 is smaller than the diameter of the inscribed circle 3.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a radiation source shutter device and a measurement device. [Background technology]

[0002] There is known a measuring device that measures plate thickness using radiation. The measuring device includes a radiation source shutter device that has a radiation source and switches between emitting and blocking the radiation source, and a detection device that detects the emitted radiation. The plate thickness of the measured object is calculated by passing the measured object between the radiation source shutter device and the detection device and measuring the transmission attenuation of the radiation in the measured object.

[0003] The radiation source shutter device provided in the measuring device is exemplified by a configuration including a housing, a holder housed inside the housing, and a capsule held by the holder (for example, Non-Patent Document 1). The holder has a recess into which the capsule is inserted. The capsule is filled with, for example, a nuclide that emits β rays: 85kr. The holder holding the capsule is rotatably supported inside the housing. The housing has a through hole formed at a position that overlaps with the capsule at a specific rotational position of the holder. In the radiation source shutter device, radiation is emitted through the through hole when the holder is rotated to a specific rotational position, and is blocked by the housing at other rotational positions and is not emitted. [Prior art documents] [Patent documents]

[0004] [Non-Patent Document 1] “6-5-1-4 Safety of radiation source containers | Japan Electrical Measuring Instruments Manufacturers' Association”, [online], [searched June 29, 2023], Internet<https: / / www.jemima.or.jp / tech / 6-05-01-04.html> Summary of the Invention [Problem to be solved by the invention]

[0005] The holder is supported by a bearing inside the housing. The diameter of the bearing is smaller than the size of the holder, and the thickness of the wall between the recess and the outer surface at the portion where the bearing is fitted is thinner than other portions. The portion where the wall is thinner has a lower radiation shielding property. On the other hand, if the bearing is moved away from the recess in order to secure the wall thickness, the radiation source shutter device will become larger.

[0006] An object of the present invention is to provide a radiation source shutter device that can ensure a sufficient wall thickness of a rotatably supported holding portion while also achieving a compact device. [Means for solving the problem]

[0007] The radiation source shutter device according to the present invention comprises a housing having an accommodation space formed therein, a holder housed in the accommodation space and having a recess formed on its outer peripheral surface, a radiation source capsule inserted into the recess, and a bearing supporting the holder on the housing so as to be rotatable around a rotation axis extending so as not to overlap with an entrance of the recess, the housing having a through hole formed therein which overlaps with part of a trajectory of the entrance of the recess when the holder rotates, the bearing does not overlap with an inscribed circle virtually inscribed in the housing when viewed from a direction perpendicular to the rotation axis, but rather part of the inscribed circle fits inside the bearing, and the inner diameter of the bearing is smaller than the diameter of the inscribed circle. Effect of the Invention

[0008] According to the present invention, it is possible to obtain a radiation source shutter device that can ensure the thickness of the wall of the rotatably supported holding portion while also achieving a compact device. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a schematic configuration of a measurement device according to a first embodiment. [Diagram 2] 1 is a front view showing a schematic configuration of a radiation source shutter device according to a first embodiment. [Diagram 3]1 is a perspective view showing a schematic configuration of a radiation source shutter device according to a first embodiment. [Figure 4] FIG. 3 is a cross-sectional view of the radiation source shutter device taken along line IV-IV shown in FIG. 2. [Diagram 5] FIG. 5 is a cross-sectional view of the radiation source shutter device taken along line VV shown in FIG. 4. [Figure 6] 4 is a cross-sectional view of the radiation source shutter device taken along line IV-IV shown in FIG. 2, illustrating a state in which a holder is in a shielding position. FIG. [Figure 7] FIG. 11 is a perspective view showing an internal configuration of a radiation source shutter device according to a modified example of the first embodiment. [Figure 8] FIG. 5 is a cross-sectional view of a radiation source shutter device according to a modified example of the first embodiment, which corresponds to the cross-sectional view taken along line VV shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a radiation source shutter device and a measurement device according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment described below.

[0011] [Embodiment 1] 1 is a perspective view showing a schematic configuration of a measurement device according to embodiment 1. The measurement device 1 includes a frame 10, a radiation source shutter device 20, and a detection device 30. The frame 10 is a frame-shaped member having a lower frame 10a and an upper frame 10b, with the lower frame 10a and the upper frame 10b being connected to each other at their ends. The region between the lower frame 10a and the upper frame 10b is a measurement space in which the thickness of an object 50 to be measured is measured.

[0012] The radiation source shutter device 20 is attached to the lower frame 10a. The detection device 30 is attached to the upper frame 10b. A gap is provided between the radiation source shutter device 20 and the detection device 30, and the object to be measured 50 moves in the direction indicated by the arrow X and passes through the gap.

[0013] Fig. 2 is a front view showing a schematic configuration of the radiation source shutter device according to the embodiment 1. Fig. 3 is a perspective view showing a schematic configuration of the radiation source shutter device according to the embodiment 1.

[0014] As shown in Fig. 2 and Fig. 3, the outer shell of the radiation source shutter device 20 is composed of a housing 21. In Fig. 3, the housing 21 is indicated by a dashed line to also show the internal configuration of the radiation source shutter device 20. An accommodation space 21a is formed inside the housing 21. A through hole 21b is formed in the housing 21 to communicate the accommodation space 21a with the outside. The housing 21 is made of a heavy metal. The heavy metal is, for example, tungsten, tungsten alloy, copper tungsten, lead, lead alloy, stainless steel, brass, or copper.

[0015] The radiation source shutter device 20 includes, in addition to the housing 21, a holder 22, a radiation source capsule 23, and a bearing 24. The holder 22 is housed in the housing space 21a. The holder 22 is supported rotatably about a rotation axis 2 inside the housing space 21a.

[0016] 4 is a cross-sectional view of the radiation source shutter device taken along line IV-IV in FIG. 2. A recess 22a recessed toward the center is formed on the outer circumferential surface of the holder 22. The rotating shaft 2 extends so as not to overlap with an entrance 22b of the recess 22a. This allows the position and orientation of the entrance 22b of the recess 22a to be changed by rotating the holder 22 about the rotating shaft 2. The holder 22 is made of a heavy metal. The heavy metal is, for example, tungsten, tungsten alloy, copper tungsten, lead, lead alloy, stainless steel, brass, or copper.

[0017] The radiation source capsule 23 serves as a radiation source that emits radiation. The radiation source capsule 23 is, for example, a sealed container in which a radioactive gas is sealed. For example, the radioactive gas is a nuclide that emits β rays: 85kr. For example, the sealed container is a capsule made of beryllium. The radiation source capsule 23 is housed in a recess 22a formed in the holder 22. Since the holder 22 is made of a heavy metal, most of the radiation emitted from the radiation source capsule 23 cannot penetrate the holder 22. On the other hand, at the entrance 22b of the recess 22a, the radiation source capsule 23 is not covered with a heavy metal, so radiation is emitted from the entrance 22b. As described above, the position and direction of the entrance 22b change with the rotation of the holder 22, and therefore the position and direction from which radiation is emitted change with the rotation of the holder 22.

[0018] Through hole 21b formed in container 21 that houses holder 22 is formed at a position that overlaps with part of the trajectory of entrance 22b that moves with the rotation of holder 22. Because container 21 is made of heavy metal, radiation emitted from entrance 22b cannot pass through container 21. Therefore, radiation is emitted to the outside of container 21 through through hole 21b only when holder 22 is in a rotational position where entrance 22b and through hole 21b overlap. In the following description, the rotational position of holder 22 when radiation is emitted is referred to as the emission position.

[0019] On the other hand, when holder 22 is in a rotational position where entrance 22b and through-hole 21b do not overlap, radiation is blocked by holder 33 and is not emitted from container 21. In the following description, the rotational position of holder 22 when radiation is not emitted is referred to as the shielding position. Note that, in order to protect radiation source capsule 23, through-hole 21b may be covered with a member that is permeable to radiation. For example, through-hole 21b may be covered with a resin film onto which aluminum is vapor-deposited.

[0020] The radiation is generated during the process of natural decay of the radioactive nuclide sealed in the radiation source capsule 23. Since the natural decay of the radioactive nuclide cannot be suppressed, the emission of radiation cannot be stopped by stopping the natural decay. Therefore, as described above, in the radiation source shutter device 20, the radiation source capsule 23 is accommodated in the recess 22a of the holder 22, and radiation is emitted only at the emission position where the entrance 22b of the recess 22a overlaps with the through-hole 21b, thereby controlling the emission and shielding of radiation.

[0021] Fig. 5 is a cross-sectional view of the radiation source shutter device taken along line VV shown in Fig. 4. The bearing 24 is a rolling bearing having an outer ring 24a and an inner ring 24b that are rotatable relative to each other. As shown in Fig. 5, the accommodation body 21 and the holder 22 are connected via the bearing 24, so that the holder 22 is rotatably supported inside the accommodation space 21a. The holder 22 has a cantilever structure supported by one bearing 24.

[0022] A recess 21c into which the outer ring 24a fits is formed in the container 21. A protrusion 22c into which the inner ring 24b fits is formed in the holder 22. Here, a circle virtually inscribed in the holder 22 when viewed from a direction perpendicular to the rotation shaft 2 is defined as an inscribed circle 3.

[0023] The bearing 24 is formed with a diameter that does not overlap with the inscribed circle 3. Moreover, the bearing 24 is provided so that a part of the inscribed circle 3 enters inside the inner ring 24b. Moreover, the inner diameter R1 of the bearing 24 (the inner diameter of the inner ring 24b) is smaller than the diameter R2 of the inscribed circle 3.

[0024] A driving unit 4 is attached to the radiation source shutter device 20. The driving unit 4 is, for example, an electric motor, and a driving shaft 4a is connected to a holder 22. The driving shaft 4a extends coaxially with the rotation shaft 2. When the driving shaft 4a of the driving unit 4 rotates, the holder 22 rotates about the rotation shaft 2.

[0025] Fig. 6 is a cross-sectional view of the radiation source shutter device taken along line IV-IV in Fig. 2, showing a state where the holder is in the shielding position, while Fig. 4, which is a similar cross-sectional view, shows a state where the holder 22 is in the emitting position.

[0026] In the radiation source shutter device 20, the holder 22 is switched between an emission position (see FIG. 4) and a shielding position (see FIG. 6) by the drive unit 4, so that the device is switched between a state in which radiation is emitted and a state in which radiation is not emitted.

[0027] Returning to FIG. 1, the radiation source shutter device 20 is attached to the lower frame 10 a of the frame 10 with the through-hole 21 b facing the detection device 30 .

[0028] The detection device 30 detects the amount of radiation radiated from the radiation source shutter device 20. The detection device 30 transmits the detected amount of radiation to a control device (not shown). The detection device is attached to the upper frame 10b of the frame 10 with a detection unit (not shown) that detects radiation facing the radiation source shutter device 20.

[0029] The radiation source shutter device 20 and the detection device 30 move along the longitudinal direction (the direction indicated by the arrow Y) of the lower frame 10a and the upper frame 10b while facing each other. By moving the radiation source shutter device 20 and the detection device 30 while passing the object 50 through the gap between the radiation source shutter device 20 and the detection device 30, it is possible to transmit radiation to the object 50 over a wide range and measure the object 50.

[0030] The object 50 to be measured is, for example, an electrode sheet used in a battery. For example, in an electrode sheet used for a positive electrode, a slurry is thinly and uniformly coated on the surface of an aluminum foil, and then dried in the next process. After drying, a similar coating is applied to the back side of the aluminum foil, and then dried. Inspections in this coating-drying process include measurement of the basis weight (coated basis weight), shape measurement of the edge of the coated portion, and image diagnosis of the dried surface condition.

[0031] In the measuring device 1 according to the first embodiment, the basis weight (coating basis weight) of the object 50 is measured. During measurement, radiation is emitted from the radiation source shutter device 20, with the holder 22 in the emission position, towards the object 50. The amount of attenuation of the radiation due to transmission through the object 50 is calculated from the amount of radiation detected by the detection device 30. The basis weight of the object 50 is calculated by comparing the amount of attenuation of the radiation with a reference attenuation obtained by measuring the attenuation of a plurality of samples, each having a known basis weight. When the object 50 is not being measured, the holder 22 is in the shielding position and no radiation is emitted from the radiation source shutter device 20.

[0032] The radiation source shutter device 20 needs to prevent radiation from leaking when it is not measuring the object 50. It also needs to prevent the capsule from being exposed and radiation from leaking in the event of a fire. The ability to prevent radiation from leaking largely depends on the wall thickness of the holder 22.

[0033] As shown in FIG. 5, the bearing 24 does not overlap the inscribed circle 3 of the holder 22. For example, when a bearing smaller in diameter than the bearing 24 is used, as in the imaginary bearing 25 shown by the two-dot chain line in FIG. 5, the imaginary bearing 25 and the inscribed circle 3 overlap. When the imaginary bearing 25 and the inscribed circle 3 overlap, the wall of the holder 22 becomes thin at the portion where the imaginary bearing 25 fits. Therefore, the thin wall portion may become a weak point in preventing radiation leakage. Therefore, when a small-diameter bearing such as the imaginary bearing 25 is provided at a position not overlapping the inscribed circle 3, as in the imaginary bearing 26 shown by the two-dot chain line in FIG. 5, in order to ensure the wall thickness, the holder 22 becomes large.

[0034] On the other hand, in the radiation source shutter device 20 of the first embodiment, the bearing 24 has a larger diameter than the imaginary bearing 25 but does not overlap with the inscribed circle 3, so that the wall thickness of the holder 22 can be ensured and leakage of radiation, etc. can be reliably prevented. In addition, since a part of the inscribed circle 3 is inside the bearing 24, the holder 22 can be made smaller in size in the direction along the rotation shaft 2.

[0035] In addition, since the inner diameter R1 of the bearing is smaller than the diameter R2 of the inscribed circle 3, the holder 22 can be made smaller in size also in the direction perpendicular to the rotation axis 2. By making the holder 22 smaller, the radiation source shutter device 20 can be made smaller.

[0036] In this way, in the radiation source shutter device 20 of the first embodiment, the overall wall thickness is ensured to prevent radiation leakage, while the device is made smaller. The smaller size also reduces the weight of the radiation source shutter device 20. The smaller size of the radiation source shutter device 20 also reduces the size and weight of the actuator that drives the radiation source shutter device 20 in the measuring device 1. This allows the measuring device 1 to be made smaller and lighter.

[0037] The radiation source shutter device 20 and the detection device 30 may be provided facing each other, and the radiation source shutter device 20 may be attached to the upper frame 10b, and the detection device 30 may be attached to the lower frame 10a. Also, the outer ring 24a of the bearing 24 may be fitted into the holder 22, and the inner ring 24b may be fitted into the container 21.

[0038] [Modifications] Fig. 7 is a perspective view showing an internal configuration of a radiation source shutter device according to a modified example of embodiment 1. Fig. 8 is a cross-sectional view of a radiation source shutter device according to a modified example of embodiment 1, which corresponds to the cross-sectional view taken along line VV in Fig. 4.

[0039] In the radiation source shutter device 20 according to the modified example, bearings 24 are provided on both sides of the holder 22. That is, the holder 22 has a double-supported structure in which it is supported from both sides by the two bearings 24. Although the increase in the number of bearings 24 complicates the structure and increases the processing costs of the holder 22, the structure in which the holder 22 is supported from both sides by the bearings 24 makes it possible to support the holder 22 more stably.

[0040] 〔others〕 Some examples of combinations of the disclosed technical features are set out below.

[0041] a radiation source shutter device comprising: a container having an accommodation space formed therein; a holder that is accommodated in the accommodation space and has a recess formed on an outer peripheral surface; a radiation source capsule inserted into the recess; and a bearing having an inner ring and an outer ring that are rotatable relative to one another, one of the inner ring and the outer ring being connected to the container and the other of the inner ring and the outer ring being connected to the holder, the bearing supporting the holder on the container so as to be rotatable about a rotation axis that extends so as not to overlap with an entrance of the recess, the container having a through hole that overlaps with part of a path of an entrance of the recess when the holder rotates, the bearing not overlapping with an inscribed circle that is a virtual sphere inscribed in the container, a part of the inscribed circle fits inside the bearing, and a part of an outer edge of the inscribed circle overlaps with the bearing when viewed along the rotation axis.

[0042] (2) The radiation source shutter device according to (1), wherein one bearing is provided.

[0043] (3) The radiation source shutter device according to (1), wherein two of the bearings are provided on either side of the holder.

[0044] (4) The radiation source shutter device according to any one of (1) to (3), wherein the holder is made of a heavy metal.

[0045] (5) The radiation source shutter device according to (4), wherein the heavy metal is tungsten, a tungsten alloy, copper tungsten, lead, a lead alloy, stainless steel, brass, or copper.

[0046] (6) A measuring device comprising: a radiation source shutter device according to any one of (1) to (5); a driving device which rotates the holder; a radiation detection device which is disposed facing the through hole of the radiation source shutter device with a gap provided between the radiation source shutter device and the radiation source shutter device; and a frame to which the radiation source shutter device and the radiation detection device are fixed. [Explanation of symbols]

[0047] 1. Measuring equipment 2 Rotation Axis 3 Inscribed circle 4 Drive unit 4a Drive shaft 10 Frames 10a Bottom frame 10b Upper frame 20 Radiation source shutter device 21 Containment Unit 21a Containment Space 21b Through hole 21c Recess 22 Holding body 22a Recess 22b Entrance 22c Convex 23 Radioactive Source Capsule 24 Bearings 24a Outer ring 24b Inner Circle 25,26 Virtual bearing 30 Detection Device 50 Object to be measured

Claims

1. A container having a container space formed therein; a holder that is accommodated in the accommodation space and has a recess formed on an outer circumferential surface; a radiation source capsule inserted into the recess; a bearing that supports the holder in the container so as to be rotatable around a rotation axis that extends so as not to overlap with an entrance of the recess, a through hole is formed in the container so as to overlap a part of a trajectory of an entrance of the recess when the holder rotates; the bearing does not overlap with an inscribed circle virtually inscribed in the housing when viewed from a direction perpendicular to the rotation axis, a part of the inscribed circle fits inside the bearing, and an inner diameter of the bearing is smaller than a diameter of the inscribed circle.

2. 2. The radiation source shutter apparatus of claim 1, wherein one said bearing is provided.

3. The radiation source shutter device according to claim 1 , wherein the bearings are two, one on each side of the holder.

4. 2. The radiation source shutter apparatus of claim 1, wherein the holder is made of a heavy metal.

5. 5. The radiation source shutter apparatus of claim 4, wherein the heavy metal is tungsten, a tungsten alloy, copper tungsten, lead, a lead alloy, stainless steel, brass, or copper.

6. A radiation source shutter device according to claim 1; A drive device that rotates the holder; a radiation detection device disposed opposite the through hole of the radiation source shutter device with a gap provided between the radiation detection device and the radiation source shutter device; A measuring apparatus comprising the radiation source shutter device and a frame to which the radiation detection device is fixed.

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