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 amount of attenuation of the radiation transmitted through the measured object.

[0003] An example of a radiation source shutter device provided in a measuring device is one that includes 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 formed therein into which the capsule is inserted. The capsule contains, for example, a nuclide that emits beta rays: 85kr. The holder holding the capsule is rotatably supported inside the housing. A through-hole is formed in the housing 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 so that radiation is not emitted. [Prior art documents] [Patent documents]

[0004] [Non-Patent Document 1] "6-5-1-4 Safety of Radiation Source Containers | Japan Electric Measuring Instruments Manufacturers' Association", [online], [Retrieved 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 location where the bearing is fitted is thinner than in other parts. The thinner wall portion has lower radiation shielding properties. On the other hand, if the bearing is moved away from the recess to ensure the wall thickness, the radiation source shutter device would become larger.

[0006] An object of the present invention is to provide a radiation source shutter device that can ensure the 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 internal storage space, a holder housed in the housing 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 that the holder can rotate around a rotation axis that extends so as not to overlap with the entrance of the recess, wherein the housing has a through-hole formed therein that overlaps with part of the trajectory of the entrance of the recess when the holder rotates, and the bearing does not overlap with an inscribed circle that is virtually inscribed in the housing when viewed from a direction perpendicular to the rotation axis, but rather part of the inscribed circle is inside the bearing, and the inner diameter of the bearing is smaller than the diameter of the inscribed circle. [Effects 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 explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a schematic configuration of a measurement device according to a first embodiment. [Figure 2] 1 is a front view showing a schematic configuration of a radiation source shutter device according to a first embodiment. [Figure 3]1 is a perspective view showing a schematic configuration of a radiation source shutter device according to a first embodiment. [Figure 4] 4 is a cross-sectional view of the radiation source shutter device taken along line IV-IV shown in FIG. 2. FIG. [Figure 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, showing a state in which a holder is in a shielding position. FIG. [Figure 7] FIG. 10 is a perspective view showing the 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 in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] A radiation source shutter device and a measurement device according to an embodiment of the present invention will be described in detail below 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 connected to each other at their ends. The region between the lower frame 10a and the upper frame 10b forms 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 through this gap in the direction indicated by arrow X.

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

[0014] As shown in Figures 2 and 3, the outer shell of the radiation source shutter device 20 is formed by a housing 21. In Figure 3, the housing 21 is indicated by a dashed line, thereby also showing 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, connecting the accommodation space 21a to the outside. The housing 21 is made of a heavy metal. Examples of heavy metals include tungsten, tungsten alloy, copper tungsten, lead, lead alloy, stainless steel, brass, and copper.

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

[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 peripheral surface of the holder 22. The rotation shaft 2 extends so as not to overlap with the 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 around the rotation shaft 2. The holder 22 is made of a heavy metal. Examples of heavy metals include tungsten, tungsten alloy, copper tungsten, lead, lead alloy, stainless steel, brass, and 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 beta 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. Because 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, and therefore, radiation is emitted from the entrance 22b. As described above, the position and orientation of the entrance 22b change as the holder 22 rotates, and therefore the position and direction from which radiation is emitted change as the holder 22 rotates.

[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 as holder 22 rotates. Because container 21 is made of a 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 housing 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, 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 on which aluminum is vapor-deposited.

[0020] The radiation is generated during the natural decay of the radioactive nuclide sealed in the radiation source capsule 23. Because the natural decay of the radioactive nuclide cannot be suppressed, it is not possible to stop the radiation emission by stopping the natural decay. Therefore, as described above, in the radiation source shutter device 20, the radiation source capsule 23 is housed 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 radiation emission and shielding.

[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 axis 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. The bearing 24 is also provided so that a portion of the inscribed circle 3 is inside the inner ring 24b. 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 drive unit 4 is attached to the radiation source shutter device 20. The drive unit 4 is, for example, an electric motor, and a drive shaft 4a is connected to a holder 22. The drive shaft 4a extends coaxially with the rotation shaft 2. When the drive shaft 4a of the drive unit 4 rotates, the holder 22 rotates around 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 in which the holder 22 is in the shielding position. Note that Fig. 4, which is a similar cross-sectional view, shows a state in which the holder 22 is in the emitting position.

[0026] In the radiation source shutter device 20, the drive unit 4 switches the holder 22 between an emission position (see FIG. 4) and a shielding position (see FIG. 6), thereby switching 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 emitted 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 so that a detection unit (not shown) that detects radiation faces the radiation source shutter device 20.

[0029] The radiation source shutter device 20 and the detection device 30 move along the longitudinal direction of the lower frame 10a and the upper frame 10b (the direction indicated by the arrow Y) 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, radiation can be transmitted through a wide range of the object 50, allowing measurement of 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, which is then dried in the next process. After drying, a similar coating is applied to the back side of the aluminum foil, which is then dried. Inspections during this coating and drying process include measuring the coating weight (basis weight), measuring the shape of the edge of the coated area, and performing image diagnosis of the dried surface condition.

[0031] The measuring device 1 according to the first embodiment measures the basis weight (coating basis weight) of the object 50. During measurement, radiation is emitted toward the object 50 from the radiation source shutter device 20, with the holder 22 in the emission position. 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 with known basis weights in advance. 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 leakage except when 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 leakage largely depends on the wall thickness of the holder 22.

[0033] As shown in FIG. 5, bearing 24 does not overlap with the inscribed circle 3 of holder 22. For example, if a bearing with a smaller diameter than bearing 24 is used, such as imaginary bearing 25 shown by the two-dot chain line in FIG. 5, imaginary bearing 25 will overlap with inscribed circle 3. If imaginary bearing 25 and inscribed circle 3 overlap, the wall of holder 22 will become thinner where it fits into imaginary bearing 25. This may result in the thinned wall becoming a weak point in preventing radiation leakage. Therefore, if a small-diameter bearing such as imaginary bearing 25 is provided at a position that does not overlap with inscribed circle 3, such as imaginary bearing 26 shown by the two-dot chain line in FIG. 5, in order to ensure sufficient wall thickness, holder 22 will end up becoming larger.

[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 radiation leakage, etc. can be reliably prevented. In addition, because a part of the inscribed circle 3 is inside the bearing 24, the size of the holder 22 in the direction along the rotation axis 2 can be reduced.

[0035] Furthermore, 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 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] As described above, 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 actuators and other components that drive 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 housing 21.

[0038] [Modification] Fig. 7 is a perspective view showing the 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 additional bearings 24 complicate the structure and increase 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 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 having an inner ring and an outer ring rotatably mounted relative to each other, wherein one of the inner ring and the outer ring is connected to the housing and the other of the inner ring and the outer ring is connected to the holder, and supporting the holder on the housing so that the holder can rotate about an axis of rotation that does not overlap with an entrance of the recess; wherein the housing has a through hole formed therein that overlaps with a part of a path of trajectory of the entrance of the recess when the holder rotates; and the bearing does not overlap with an inscribed circle, which is a virtual sphere inscribed in the housing, but a part of the inscribed circle is inside the bearing, and a part of an outer edge of the inscribed circle overlaps with the bearing when viewed along the axis of rotation.

[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 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: the radiation source shutter device according to any one of (1) to (5); a driving device that rotates the holder; a radiation detection device that is disposed opposite the through-hole of the radiation source shutter device with a gap provided between the radiation source shutter device and the radiation detection 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 axes 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 part 23 Radiation 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 housing body having a housing 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 that the holder can rotate 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 an inscribed circle virtually inscribed in the housing when viewed from a direction perpendicular to the rotation axis, a part of the inscribed circle is 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 device of claim 1, wherein one of the bearings is provided.

3. 2. The radiation source shutter device according to claim 1, wherein two of the bearings are provided with the holder therebetween.

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

5. 5. The radiation source shutter device according to 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 unit 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 measurement device comprising the radiation source shutter device and a frame to which the radiation detection device is fixed.

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