Inner diameter measuring unit and inner diameter measuring method

Abstract

To provide an inner diameter measuring unit which has a simple constitution, is not affected by disturbance light, can reliably measure an inner diameter of even a transparent resin container, and reduces the positional deviation of a cylindrical container.SOLUTION: An inner diameter measuring unit 110 includes an insertion body 111 that can be inserted into a cylindrical container PF, and a measuring section 125 provided inside the insertion body 111. A pair of first insertion holes 112 that open in the radial direction are provided in the end portion of the insertion body 111. A pair of first contact pieces 113 are provided in the pair of first insertion holes 112 so as to be movable forward and backward in the radial direction of the insertion body 111. The pair of first contact elements 113 are biased outward in the radial direction of the insertion body 111, and have contact portions 114 capable of protruding outward in the radial direction from the outer peripheral surface of the insertion body 111. The measuring section 125 is configured to measure the inner diameter of a mouth Pa of the cylindrical container PF based on the forward and backward movement of each of the pair of first contact elements 113 in the radial direction of the contact element 113.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inner diameter measuring unit and an inner diameter measuring method for measuring the inner diameter of the mouth of a cylindrical container. [Background technology]

[0002] BACKGROUND ART Conventionally, as an inner diameter measuring unit for measuring the inner diameter of a cylindrical container, for example, an inner diameter measuring unit (fourth dimension measuring machine 34) provided in an inspection device for can bodies described in Patent Document 1 has been known.

[0003] The inner diameter measuring unit (fourth dimension measuring machine 34) known in Patent Document 1 has an insert (measuring instrument 70) inserted into the mouth of a cylindrical container (can body 1B) whose position has been adjusted by a position adjustment body (centering mechanism 341), and the insert (measuring instrument 70) inserted into the cylindrical container (can body 1B) rotates to irradiate laser light, and a measuring element 71 receives the reflected light, and based on the received light, a calculation means calculates the inner diameter f of the cylindrical container (can body 1B). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-228136 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is still room for improvement in the known inner diameter measurement unit disclosed in Patent Document 1 and the like.

[0006] In other words, the inner diameter measurement unit known from Patent Document 1 is an inner diameter measurement device that uses the reflected light when laser light is irradiated onto the inner surface of a cylindrical container, so there is a risk that the reflected light will not be stable in transparent resin containers, etc., and the inner diameter will not be measured correctly. Furthermore, depending on the environment around the inner diameter measurement unit, there is a risk that the light receiving section may receive light other than reflected laser light due to room lighting, etc., which may cause the inner diameter measurement value to become unstable. Furthermore, since the position of the cylindrical container is adjusted on the bottom side of the cylindrical container, there was a risk that a slight positional shift on the bottom side of the cylindrical container would cause a large positional shift on the mouth side of the cylindrical container, resulting in an unstable measurement value of the inner diameter of the mouth.

[0007] The present invention aims to solve these problems and provide an inner diameter measurement unit that has a simple configuration, is not affected by ambient light, can reliably measure the inner diameter of cylindrical containers even if they are transparent resin containers, and has little positional deviation of the cylindrical container. [Means for solving the problem]

[0008] The inner diameter measurement unit of the present invention is an inner diameter measurement unit having a cylindrical insert that can be inserted into the mouth of a cylindrical container and a measuring unit provided inside the insert, wherein the outer peripheral surface of the end of the insert is provided with a pair of first insertion holes that are open in the radial direction, and each of the pair of first insertion holes is provided with a pair of first contactors that are capable of moving back and forth in the radial direction of the insert, the pair of first contactors are biased radially outward of the insert and have contact portions that can protrude radially outward beyond the outer peripheral surface of the insert, and the measuring unit is configured to be able to measure the inner diameter of the mouth of the cylindrical container based on the radial movement of each of the pair of first contactors. [Effects of the Invention]

[0009] The inner diameter measurement unit of the invention of claim 1 has a pair of first insertion holes that are open in the radial direction on the outer peripheral surface of the end of the insert, and each of the pair of first insertion holes has a pair of first contactors that are movable back and forth in the radial direction of the insert, and the pair of first contactors are biased radially outward of the insert and have contact portions that can protrude radially outward from the outer peripheral surface of the insert, and the measurement unit is configured to be able to measure the inner diameter of the mouth of a cylindrical container based on the radial movement of each of the pair of first contactors.Therefore, if the distance between the contact portions of the pair of first contactors before insertion into the cylindrical container is greater than the inner diameter of the mouth of the cylindrical container, when the insert is inserted into the cylindrical container, the pair of first contactors move into the pair of first insertion holes so that the contact portions follow the inner diameter of the mouth, and the measurement unit can measure the inner diameter of the mouth of the cylindrical container based on the amount of movement of the first contactors. Furthermore, since the inner diameter of the mouth of the cylindrical container is measured by directly contacting it with the contact part, it is not affected by ambient light, etc., as compared to optical measurement, and the inner diameter of the mouth can be measured reliably even if the cylindrical container is a transparent resin container, for example. Furthermore, if the cylindrical container is held so that it can move slightly, when the insert is inserted into the mouth of the cylindrical container, the positional deviation of the cylindrical container can be adjusted so that the biasing forces of the pair of first contacts are balanced.

[0010] According to the configuration described in claim 2, the measuring unit has a pair of measuring rods that move back and forth within the inserter in the axial direction of the inserter, and the pair of measuring rods are configured to move back and forth in the axial direction of the inserter in conjunction with the forward and backward movements of each of the pair of first contactors by a displacement switching mechanism.Therefore, even if the outer diameter of the inserter is large enough that the measuring unit cannot be directly accommodated in the forward and backward direction of the first contactors, the measuring unit can be positioned along the axial direction of the inserter to measure the amount of forward and backward movement of the first contactors. That is, the inner diameter of the mouth of a cylindrical container having a small inner diameter can be reliably measured. According to the configuration described in claim 3, a position adjustment body is provided around the insert body, which is movable relative to the insert body in the axial direction, and the lower end of the position adjustment body has an inclined surface that gradually expands radially outward as it extends upward.Therefore, for example, when the insert body is inserted into the mouth of a cylindrical container, the cylindrical container can be centered so that the central axes of the cylindrical container and the insert body are aligned by positioning the mouth so that it comes into contact with the inclined surface of the position adjustment body.

[0011] According to the configuration described in claim 4, the position adjustment body has a downwardly open notch on the inclined surface at a position that overlaps circumferentially with the formation direction of the pair of first insertion holes, and the notch is formed with a width that can accept the contact portion, and the position adjustment body is configured to be able to move relative to the insert body to a position where the contact portion is contained within the notch.Therefore, even without using the position adjustment body to push the first contactor into the first insertion hole, when inserting the insert body into the cylindrical container, the position adjustment body contacts the mouth before the first contactor, and the cylindrical container can be centered so that the central axes of the cylindrical container and the insert body are aligned. According to the configuration described in claim 5, a pair of second insertion holes are provided on the outer peripheral surface of the end of the insert, opening the insert radially outward in a direction intersecting the pair of first insertion holes, and a pair of second contactors are respectively provided in each of the pair of second insertion holes, which are movable back and forth in the radial direction of the insert, and the measuring unit is configured to be able to measure the inner diameter of the mouth of the cylindrical container based on the radial movement of each of the pair of second contactors of the insert.Therefore, by inserting the insert into the mouth of the cylindrical container, the inner diameter of the mouth can be measured in two directions at once, thereby reducing the time required to measure multiple locations within the mouth.

[0012] According to the configuration described in claim 6, the pair of second insertion holes are formed at different positions in the axial direction of the insert body from the pair of first insertion holes, so that by inserting the insert body into the mouth of the cylindrical container, the inner diameter of the mouth can be measured at different height positions at once, thereby reducing the time required to measure multiple locations within the mouth. Furthermore, since the pair of first insertion holes and the pair of second insertion holes do not intersect at the same height, the pair of first contactors and the pair of second contactors do not interfere with each other when moving forward and backward, thereby improving the accommodation efficiency of the first contactors, second contactors, and measuring part within the insertion body. According to the configuration described in claim 7, the insert is configured to be insertable into a cylindrical container with a nominal diameter of the mouth of 38 mm or less, so that the inner diameter of the mouth can be measured even for PET bottles or preforms with small inner diameters of the mouth.

[0013] According to the configuration of claim 8, the inner diameter measuring device has a holding unit, so that the inner diameter of the mouth can be reliably measured using the inner diameter measuring unit while the cylindrical container is held in an appropriate position by the holding unit, compared to when the operator holds the cylindrical container by hand. According to the configuration described in claim 9, the holding unit is configured to be movable horizontally perpendicular to the central axis of the cylindrical container held by the holding unit, so that even if the central axis of the cylindrical container held by the holding unit and the central axis of the insert of the inner diameter measurement unit are slightly misaligned, they can be moved to a position where their central axes align when inserting the insert into the cylindrical container.

[0014] According to the configuration described in claim 10, the holding unit or the insert is configured so that the cylindrical container and the insert can be rotated relative to each other, with the central axis of the cylindrical container held by the holding unit as the center of rotation.Therefore, after inserting the insert to a predetermined position in the mouth, the cylindrical container can be rotated with the holding unit, thereby easily measuring the inner diameter at multiple points at a predetermined height in the mouth. The inner diameter measurement method of the invention according to claim 11 comprises a measuring means for measuring the inner diameter of the mouth of a cylindrical container and an insertion means for inserting the measuring means into the mouth of the cylindrical container, and the measuring means measures the inner diameter of the mouth of the cylindrical container by bringing a contact means that can move back and forth radially into contact with the inner surface of the mouth of the cylindrical container. Therefore, if the radial distance of the contact means of the measuring means before it is moved to the cylindrical container by the insertion means is greater than the inner diameter of the mouth of the cylindrical container, the inner diameter of the mouth of the cylindrical container can be measured based on the amount of movement of both radial ends of the contact means so as to follow the inner diameter of the mouth when the measuring means is moved to the cylindrical container. Furthermore, since the inner diameter of the mouth of the cylindrical container is measured by directly contacting it at both radial ends of the contact means, it is not affected by ambient light, etc., as compared to optical measurement, and the inner diameter of the mouth can be reliably measured even if the cylindrical container is a transparent resin container, for example. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an overall view showing an inner diameter measurement instrument 100 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a partially enlarged cross-sectional view of an inner diameter measurement unit 110 of the inner diameter measurement instrument 100 according to one embodiment of the present invention. [Figure 3] FIG. 2 is a bottom view of the inner diameter measurement unit 110 of the inner diameter measurement instrument 100 according to one embodiment of the present invention. [Figure 4] 1 is an enlarged schematic view showing an inner diameter measurement procedure 1 of an inner diameter measurement instrument 100 according to an embodiment of the present invention. [Figure 5] FIG. 2 is an enlarged schematic view showing an inner diameter measurement procedure 2 of the inner diameter measurement instrument 100 according to one embodiment of the present invention. [Figure 6] FIG. 2 is an enlarged schematic cross-sectional view showing an inner diameter measurement procedure 2 of the inner diameter measurement instrument 100 according to one embodiment of the present invention. [Figure 7] 2 is a cross-sectional view taken along line AA' showing an inner diameter measurement procedure 2 of the inner diameter measurement instrument 100 according to one embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] An inner diameter measurement instrument 100 according to one embodiment of the present invention will be described below with reference to the drawings. For the sake of explanation, the control unit is not shown.

[0017] As shown in Figures 1 to 3, an inner diameter measurement instrument 100 according to one embodiment of the present invention has an insert 111 that can be inserted into the mouth portion Pa of a preform PF, which is a transparent cylindrical container, an inner diameter measurement unit 110 having measuring sections 125 (first measuring section 125a, second measuring section 125b, third measuring section 125c, fourth measuring section 125d) provided inside the insert 111, and a holding unit 130 that holds the preform PF.

[0018] The inner diameter measurement unit 110 includes a pair of first insertion holes 112a (insertion holes 112) that are open in the radial direction on the outer peripheral surface of the end of the insert 111, a pair of second insertion holes 112b (insertion holes 112) that are provided above the pair of first insertion holes 112a (insertion holes 112) and in a direction that intersects with the pair of first insertion holes 112a, first contacts 113 (1a contacts 113a, 1b contacts 113b) that are contacts that are provided so as to be able to advance and retreat in the pair of first insertion holes 112a, and first contacts 113 that are provided so as to be able to advance and retreat in the pair of second insertion holes 112b. The insert 111 has a second contactor 114 (second a contactor 114a, second b contactor 114b), a measuring rod 126 (first measuring rod 126a, second measuring rod 126b, third measuring rod 126c, fourth measuring rod 126d) that moves back and forth within the insert 111 in the axial direction of the insert 111, a displacement switching mechanism 127 formed by the contact portions between the first contactor 113 and the second contactor 114 and the measuring rod 126, and a position adjustment body 120 provided around the insert 111 and biased downward by a pressing spring Sa. The first insertion hole 112a and the second insertion hole 112b are disposed at different positions (heights) in the axial direction of the insert 111.

[0019] The angle at which the first insertion hole 112a and the second insertion hole 112b intersect is preferably 90°, but may be any other angle. Furthermore, if the first insertion hole 112a and the second insertion hole 112b are provided at different heights in directions that intersect with each other, even if the insert 111 is formed thin, the first contactor 113, the second contactor 114, and each measuring rod 126 can be positioned without interfering with each other. This allows the insert 111 to be inserted into a narrow measurement target such as the mouth portion Pa of the preform PF to measure the inside diameter. The nominal diameter of the mouth portion Pa of the preform PF is generally 28 mm, 30 mm, 38 mm, etc., and the insert 111 is preferably configured so as to be insertable into the mouth portion Pa having a nominal diameter of 38 mm or less. The nominal diameter refers to the outer diameter of the thread formed on the mouth portion Pa, with a nominal diameter of 28 mm being an inner diameter of approximately 20 to 22 mm, a nominal diameter of 30 mm being an inner diameter of approximately 24.5 to 25.5 mm, and a nominal diameter of 38 mm being an inner diameter of approximately 30 to 31 mm.

[0020] The holding unit 130 receives the body portion Pb of the preform PF in the holding hole 131, supports the flange Pd of the preform PF from below, and holds the bottom portion Pc so that it is raised.

[0021] The first contactor 113 (1a contactor 113a, 1b contactor 113b) and the second contactor 114 (2a contactor 114a, 2b contactor 114b) have spherical 1a contact portion 113a1, 1b contact portion 113b1, 2a contact portion 114a1, and 2b contact portion 114b1 at their tips, respectively, and are biased toward the opening sides of a pair of first insertion holes 112a (insertion holes 112) and a pair of second insertion holes 112b (insertion holes 112) by a protruding spring Sb. The first contactor 113 and the second contactor 114 are configured to be movable to a position where the length between both ends of the 1a contact portion 113a1 and the 1b contact portion 113b1, and the length between both ends of the 2a contact portion 114a1 and the 2b contact portion 114b1 are slightly larger than the inner diameter of the mouth portion Pa of the preform PF. The displacement switching mechanism 127 has the tip of the measuring rod 126 in contact with the inclined portion provided on the upper part of the first contactor 113 and the second contactor 114, and can move the measuring rod 126 back and forth along the axial direction of the insert 111 along the inclined portion that moves as the first contactor 113 and the second contactor 114 move back and forth.

[0022] The lower part of the position adjustment body 120 is provided with an inclined surface 121 which gradually widens radially outward as it extends upward, and at a position which overlaps circumferentially with the formation direction of the pair of insertion holes 112, a downwardly open notch 122 is provided, and the notch 122 is formed with a width which can accommodate the 1a contact portion 113a1, the 1b contact portion 113b1, the 2a contact portion 114a1, and the 2b contact portion 114b1. As a result, when the insert 111 is inserted into the mouth portion Pa of the preform PF, the mouth portion Pa contacts the inclined surface 121 of the position adjustment body 120 before the 1a contact portion 113a1 and the 1b contact portion 113b1, and the central axis can be aligned with that of the preform PF. The control unit is configured to be able to communicate with the measuring unit 125, and is configured to be able to calculate the inner diameter of the mouth portion Pa of the preform PF from the amount of displacement of each of the measuring rods 126 connected to the measuring unit 125.

[0023] Next, a method for measuring the inner diameter of the mouth of a preform PF using the inner diameter measurement instrument 100 according to an embodiment of the present invention will be described with reference to FIGS.

[0024] First, the preform PF is inserted into the holding hole 131 of the holding unit 130, so that the holding unit 130 supports the flange Pd and holds the preform PF. Next, the inner diameter measurement unit 110 waiting above is aligned with the central axis of the preform PF held by the holding unit 130, and is lowered using an insertion means (not shown) to insert the lower end of the insert 111 into the mouth portion Pa of the preform PF.

[0025] When the inner diameter measuring unit 110 is further lowered, the inclined surface 121 of the position adjusting body 120 comes into contact with the upper surface of the mouth portion Pa of the preform PF. At this time, if the holding unit 130 is configured to be movable horizontally, the holding unit 130 can be adjusted by slightly moving its horizontal position so that the entire circumference of the inclined surface 121 comes into contact with the upper surface of the mouth portion Pa of the preform PF. That is, since the holding unit 130 holds the preform PF so that it can move horizontally, it is possible to reliably eliminate any misalignment between the central axes of the insert 111 and the preform PF.

[0026] When the insert 111 is further lowered, the position adjuster 120 that interferes with the upper surface of the mouth Pa does not move, and only the insert 111 advances further into the mouth Pa while compressing the pressing spring Sa. As a result, the first contact 113 and the second contact 114 move from the notch 122 and come into contact with the inner circumferential surface of the opening portion Pa. Since the 1a contact portion 113a1, the 1b contact portion 113b1, the 2a contact portion 114a1, and the 2b contact portion 114b1 are each formed in a spherical shape, when they come into contact with the mouth portion Pa, they can be smoothly pressed in the opposite direction to the biasing direction of the protruding spring Sb, so that the upper surface and inner surface of the mouth portion Pa are not damaged.

[0027] The first contactor 113 and the second contactor 114 convert the displacement caused by the 1a contactor 113a, the 1b contactor 113b, the 2a contactor 114a, and the 2b contactor 114b, respectively, hitting the inner surface of the mouth portion Pa and being pushed into the insertion hole 122 into axial displacement of the measuring rod 126 (first measuring rod 126a, second measuring rod 126b, third measuring rod 126c, fourth measuring rod 126d) by the displacement switching mechanism 127. The measurement unit 125 (first measurement unit 125a, second measurement unit 125b, third measurement unit (not shown), fourth measurement unit (not shown)) sends the displacement of the measurement rod 126 (first measurement rod 126a, second measurement rod 126b, third measurement rod 126c, fourth measurement rod 126d) to the control unit (not shown).

[0028] The control unit (not shown) calculates the inner diameter (length between L1-L1') of the mouth portion Pa at the point where the first contactor 113 contacts from the displacement amount of the first measuring rod 126a and the second measuring rod 126b, and calculates the inner diameter (length between U1-U1') of the mouth portion Pa at the point where the second contactor 114 contacts from the displacement amount of the third measuring rod 126c and the fourth measuring rod 126d. This makes it possible to measure the inner diameters at different height positions on the inner peripheral surface of the mouth portion Pa of the preform PF at the same time.

[0029] Here, by simply rotating the insert 111 by 90 degrees without changing the amount of penetration of the insert 111 into the preform PF, the inner diameters (length between L2-L2', length between U2-U2') at different circumferential positions at the heights initially measured with the first contactor 113 and the second contactor 114 can be easily measured.

[0030] As described above, by simply inserting the insert 111 of the inner diameter measurement unit 110 into the preform PF held in the holding unit 130, it is possible to quickly and easily accurately measure a small inner diameter such as the mouth portion Pa of the preform PF. Furthermore, the inner diameter of a transparent cylindrical container, which is difficult to measure stably using optical measurement methods, can be reliably measured.

[0031] Furthermore, by changing the positions of the first contactor 113 and the second contactor 114 and the length of the insert 111, it is possible to simultaneously and continuously measure the inner diameter of the cylindrical container at various positions.

[0032] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various design modifications can be made without departing from the present invention as set forth in the claims.

[0033] In the above-described embodiment, the holding unit is described as holding the preform by supporting the flange of the preform and being configured to be slightly movable horizontally, but the configuration of the holding unit is not limited to this. For example, the bottom of the preform may be held by being supported by the bottom surface of the holding hole, or the body of the preform may be gripped by claw-like holding claws. The holding unit may not move horizontally, but the inner diameter of the holding hole may be formed slightly larger than the outer diameter of the preform, allowing the preform to move slightly horizontally within the holding hole. The holding unit may also be configured to be rotatable around the central axis of the holding hole as the rotation axis. Furthermore, in the above-described embodiment, the inner diameter measuring device was described as holding a preform with a holding unit and measuring the inner diameter of the mouth of the preform with an inner diameter measuring unit, but the configuration of the inner diameter measuring device is not limited to this. For example, the holding unit may be configured to be able to hold a PET bottle and to be able to measure the inner diameter of the mouth of the PET bottle, and may also be applied to other transparent or opaque containers such as glass bottles, plastic cups, and tubes.

[0034] Furthermore, the above-described embodiment has been described as measuring the inner diameter of a preform at two locations simultaneously using a first contactor and a second contactor arranged at different heights and rotated 90 degrees, but the number of inner diameters measured simultaneously and the measurement locations are not limited to this. For example, the first contactor may not be necessary, and a third pair of contactors may be provided above the second contactor and arranged at a 45-degree angle from the first and second contactors, allowing the inner diameter to be measured at three locations simultaneously. Furthermore, in the above-described embodiment, the 1a contact portion, the 1b contact portion, the 2a contact portion, and the 2b contact portion are described as being formed in a spherical shape, but the shapes of the 1a contact portion, the 1b contact portion, the 2a contact portion, and the 2b contact portion are not limited to this, and may be formed in, for example, a truncated cone shape, or may be formed in a curved shape from top to bottom.

[0035] Furthermore, in the above-described embodiment, it has been described that the mouth portion comes into contact with the inclined surface of the position adjustment body, and the central axis can be aligned with that of the preform, but the method of centering the preform is not limited to this. For example, it is also possible to align the central axes of the insert and preform by moving the inner diameter measurement unit or the holding unit horizontally based on an image of the mouth portion of the preform held by the holding unit, without providing a position adjustment body, or to align the central axes of the insert and preform by using the difference in the biasing force of the protruding spring that biases the measuring probe. [Explanation of symbols]

[0036] 100 ··· Inner diameter measuring device 110 ··· Inner diameter measurement unit 111 Insert 112 Insertion hole 112a First insertion hole 112b Second insertion hole 113 First contact 113a... Contact 1a 113a1 ··· 1a contact part 113b 1b contact 113b1 ··· 1b contact part 114 Second contact 114a... 2nd a contact 114a1... 2nd a contact part 114b 2nd contactor 114b1 ··· 2b contact part 120 ... position adjustment body 121... Slope 122 Notch 125... Measuring section 125a... 1st measurement section 125b... 2nd measurement section 125c... 3rd measurement section 125d... 4th measurement section 126 Measuring rod 126a First measuring rod 126b Second measuring rod 126c Third measuring rod 126d 4th measuring rod 127 Displacement switching mechanism 130 Holding unit 131... Retaining hole PF ··· Preform (cylindrical container) Pa... Mouth Pb Body PC...Bottom Pd ··· Flange Sa ··· Press spring Sb: Projecting spring L1, L1', L2, L2': Measurement points on the lower contact area U1, U1', U2, U2'...Upper contact measurement points

Claims

1. An inner diameter measurement unit having a cylindrical insert that can be inserted into the mouth of a cylindrical container and a measurement unit provided inside the insert, a pair of first insertion holes that are open in the radial direction are provided on the outer peripheral surface of the end of the insert; The pair of first insertion holes are respectively provided with first contacts, which are a pair of contacts provided so as to be movable forward and backward in the radial direction of the insert body, the pair of first contacts are biased radially outward of the insert body and have contact portions that can protrude radially outward beyond the outer circumferential surface of the insert body; An inner diameter measuring unit characterized in that the measuring unit is configured to be able to measure the inner diameter of the mouth of a cylindrical container based on the radial forward and backward movement of each of the pair of first contactors.

2. the measuring unit has a pair of measuring rods that move back and forth in the axial direction of the insert body within the insert body, The inner diameter measurement unit according to claim 1, characterized in that the pair of measuring rods are configured to move back and forth in the axial direction of the insert body in conjunction with the respective forward and backward movements of the pair of first contactors by a displacement switching mechanism.

3. a position adjustment body that is movable relative to the insert in the axial direction is provided around the insert, 2. The inner diameter measurement unit according to claim 1, wherein the lower end of the position adjustment body has an inclined surface whose diameter gradually increases radially outward as it extends upward.

4. the position adjuster has a notch portion that is open downward on the inclined surface at a position that circumferentially overlaps with a direction in which the pair of first insertion holes are formed, the notch is formed with a width that allows the contact portion to be received therein; 4. The inner diameter measurement unit according to claim 3, wherein the position adjuster is configured to be movable relative to the insert to a position where the contact portion is contained within the notch.

5. a pair of second through-holes that open radially outward from the insert in a direction intersecting the pair of first through-holes, the second through-holes being provided on the outer peripheral surface of the end of the insert; A pair of second contacts are provided in the pair of second insertion holes, respectively, and are movable forward and backward in the radial direction of the insert body, The inner diameter measurement unit according to claim 1, characterized in that the measurement unit is configured to be able to measure the inner diameter of the mouth of a cylindrical container based on the radial movement of each of the pair of second contacts of the insert.

6. 6. The inner diameter measurement unit according to claim 5, wherein the pair of second insertion holes are formed at positions different from the pair of first insertion holes in the axial direction of the insert.

7. 2. The inner diameter measurement unit according to claim 1, wherein the cylindrical container is a PET bottle or a preform, and the insert is configured to be insertable into a cylindrical container having a nominal diameter of the opening of 38 mm or less.

8. An inner diameter measuring device comprising the inner diameter measuring unit according to claim 1 and a holding unit for holding a cylindrical container.

9. 9. The inner diameter measuring device according to claim 8, wherein the holding unit is configured to be able to move the cylindrical container held by the holding unit in a horizontal direction perpendicular to the central axis of the cylindrical container.

10. 9. The inner diameter measuring instrument according to claim 8, wherein the holding unit or the insert is configured so that the cylindrical container and the insert can rotate relative to each other around the central axis of the cylindrical container held by the holding unit.

11. An inner diameter measurement method comprising a measuring means for measuring the inner diameter of a mouth of a cylindrical container and an inserting means for inserting the measuring means into the mouth of the cylindrical container, The inner diameter measuring method is characterized in that the measuring means measures the inner diameter of the mouth of the cylindrical container by bringing a contact means that is movable back and forth in the radial direction into contact with the inner surface of the mouth of the cylindrical container.

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