Method and apparatus for drawing glass preform

Abstract

To further prevent a yield from reducing when forming a plurality of drawn preforms from a glass preform.SOLUTION: A method for drawing a glass preform, capable of forming a drawn body having a plurality of drawn preforms obtained by drawing the glass preform while heating the glass preform by a heating furnace comprises steps of: measuring the outer diameter of the drawn body while drawing the glass preform to control the outer diameter so that the outer diameter measurement value is coincident with a target outer diameter value; acquiring at least one of the outer-diameter measurement value and the imaged image of the drawn body in association with a longitudinal position of the drawn body while drawing the glass preform; performing abnormality determination for determining the existence of an abnormal part in the drawn body on the basis of the at least one of the outer diameter measurement value and the imaged image of the drawn body in association with the longitudinal position of the drawn body; and determining a division position dividing the drawn body into the plurality of drawn preforms on the basis of the result of abnormality determination after drawing the glass preform.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for elongating a glass preform and an apparatus for elongating a glass preform. [Background technology]

[0002] Patent Document 1 discloses a method for elongating a glass preform for optical fiber while heating it. An upper chuck and a lower chuck, which hold both ends of the glass preform, are moved at different speeds while the glass preform is heated, thereby forming an elongated body of the glass preform. The formed elongated body is then divided into a plurality of elongated preforms. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-87338 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the occurrence of abnormalities in the glass base material or the elongated body may result in the elongated base material obtained from the elongated body being shorter than the specified length or in an excess portion of the elongated body, resulting in a decrease in yield.

[0005] An object of the present disclosure is to further suppress a decrease in yield when forming a plurality of elongated preforms from a glass preform. [Means for solving the problem]

[0006] The method for elongating a glass preform according to the present disclosure includes: A method for elongating a glass preform, in which a glass preform is elongated while being heated in a heating furnace to form an elongated body from which a plurality of elongated preforms are obtained, comprising the steps of: measuring an outer diameter of the elongated body during elongation of the glass preform, and controlling the measured outer diameter to match a target outer diameter value; acquiring at least one of the outer diameter measurement value and an image of the elongated body in association with a longitudinal position of the elongated body during elongation of the glass preform; performing an abnormality determination step of determining whether or not there is an abnormal portion in the elongated body based on at least one of the outer diameter measurement value and the captured image associated with the longitudinal position of the elongated body; After the elongation of the glass preform is completed, determining division positions for dividing the elongated body into a plurality of the elongated preforms based on the result of the abnormality determination; Includes:

[0007] The glass base material elongation device of the present disclosure comprises: A glass preform elongation apparatus for forming an elongated body in which a plurality of elongated preforms are obtained by elongating a glass preform while heating it in a heating furnace, comprising: a control device that measures the outer diameter of the elongated body during elongation of the glass base material and controls the measured outer diameter to match a target outer diameter value; a processing device that acquires at least one of the outer diameter measurement value and an image of the elongated body in association with a longitudinal position of the elongated body during elongation of the glass base material, The processing device includes: performing an abnormality determination to determine whether or not there is an abnormal portion in the elongated body based on at least one of the outer diameter measurement value and the captured image associated with the longitudinal position of the elongated body; After the elongation of the glass base material is completed, division positions for dividing the elongated body into a plurality of elongated base materials are determined based on the result of the abnormality determination. [Effects of the Invention]

[0008] According to the present disclosure, a decrease in yield can be suppressed when forming a plurality of elongated base materials from a glass base material. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a glass base material elongating apparatus according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram for explaining the problem that occurs when dividing the elongated body shown in FIG. [Figure 3] FIG. 3 is a schematic diagram (part 1) for explaining the dividing positions of the elongated body determined by the server shown in FIG. [Figure 4] FIG. 4 is a schematic diagram (part 2) for explaining the dividing positions of the elongated body determined by the server shown in FIG. [Figure 5] FIG. 5 is a schematic diagram (part 3) for explaining the dividing positions of the elongated body determined by the server shown in FIG. [Figure 6] FIG. 6 is a flowchart showing the flow of operations when the stretching device shown in FIG. 1 stretches the stretched body and determines the division positions. [Figure 7] FIG. 7 is a flowchart (part 1) showing the flow of the division position determination process shown in FIG. [Figure 8] FIG. 8 is a flowchart (part 2) showing the flow of the division position determination process shown in FIG. [Figure 9] FIG. 9 is a flowchart (part 3) showing the flow of the division position determination process shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Description of the embodiments of the present disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. The method for elongating a glass preform according to the present disclosure includes: (1) A method for elongating a glass preform by elongating a glass preform while heating it in a heating furnace to form an elongated body from which a plurality of elongated preforms can be obtained, measuring an outer diameter of the elongated body during elongation of the glass preform, and controlling the measured outer diameter to match a target outer diameter value; acquiring at least one of the outer diameter measurement value and an image of the elongated body in association with a longitudinal position of the elongated body during elongation of the glass preform; performing an abnormality determination step of determining whether or not there is an abnormal portion in the elongated body based on at least one of the outer diameter measurement value and the captured image associated with the longitudinal position of the elongated body; After the elongation of the glass preform is completed, determining division positions for dividing the elongated body into a plurality of the elongated preforms based on the result of the abnormality determination; Includes:

[0011] As described above, by determining whether or not there is an abnormality in the elongated body before dividing the elongated body into a plurality of elongated base materials, it is possible to determine the dividing positions of the elongated body so as to reduce the amount of elongated body or elongated base materials that are discarded, compared to a method in which the presence or absence of an abnormality is determined after division, thereby suppressing a decrease in yield.

[0012] (2) In the method for elongating a glass base material described in (1) above, At least one of the outer diameter measurement value and the captured image associated with the longitudinal position of the elongated body is stored in a storage device; In the step of making the abnormality determination, the abnormality determination may be made based on at least one of the outer diameter measurement value and the captured image stored in the storage device.

[0013] According to the above method, the worker does not need to monitor the drawn body in real time during drawing, which reduces the burden on the worker.

[0014] (3) In the method for elongating a glass base material according to (1) or (2), When the abnormality determination is performed based on the captured image, If the average brightness of the captured image exceeds a predetermined threshold, it may be determined that there is an abnormality in the elongated body.

[0015] According to the above-described method, it is possible to automatically determine whether an abnormality such as an internal bubble or a surface scratch exists in the elongated body.

[0016] (4) In the method for elongating a glass base material according to any one of (1) to (3) above, In the step of determining the division position, When the stretched base material is cut to a predetermined length from a first end of a normal part excluding the abnormal part of the stretched body, if the remaining length after cutting is equal to or greater than the minimum length of the stretched base material, the position at the predetermined length from the first end may be determined as the division position, and if the remaining length after cutting is less than the minimum length of the stretched base material, the middle of the normal part may be determined as the division position.

[0017] According to the above method, while ensuring as much stretched base material of a predetermined length as possible, the amount of waste stretched body or stretched base material can be reduced by appropriately switching from obtaining stretched base material of a predetermined length to obtaining stretched base material of a length that is equal to or greater than the minimum length but less than the predetermined length, depending on the length of the normal part of the stretched body.

[0018] The glass base material elongation device of the present disclosure comprises: (5) A glass preform elongation apparatus for forming an elongated body from which a plurality of elongated preforms are obtained by elongating a glass preform while heating it in a heating furnace, a control device that measures the outer diameter of the elongated body during elongation of the glass base material and controls the measured outer diameter to match a target outer diameter value; a processing device that acquires at least one of the outer diameter measurement value and an image of the elongated body in association with a longitudinal position of the elongated body during elongation of the glass base material, The processing device includes: performing an abnormality determination to determine whether or not there is an abnormal portion in the elongated body based on at least one of the outer diameter measurement value and the captured image associated with the longitudinal position of the elongated body; After the elongation of the glass base material is completed, division positions for dividing the elongated body into a plurality of elongated base materials are determined based on the result of the abnormality determination.

[0019] As described above, by determining whether or not there is an abnormality in the elongated body before dividing the elongated body into a plurality of elongated base materials, it is possible to determine the dividing positions of the elongated body so as to reduce the amount of elongated body or elongated base materials to be discarded, compared to a configuration in which the presence or absence of an abnormality is determined after division, thereby suppressing a decrease in yield.

[0020] [Details of the embodiments of the present disclosure] Specific examples of a glass preform elongation method and a glass preform elongation apparatus according to embodiments of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. In addition, the scales of the drawings used in the following description have been appropriately changed to make each component recognizable.

[0021] (Glass base material elongation device) FIG. 1 is a schematic diagram showing the configuration of an elongation apparatus 1 for a glass preform G according to the present embodiment. The elongation apparatus 1 is configured to elongate the glass preform G while heating it, thereby forming an elongated body G1 having a diameter smaller than that of the glass preform G. The elongated body G1 formed by the elongation apparatus 1 is divided at predetermined positions in the longitudinal direction, as described below, to obtain a plurality of elongated preforms. The glass preform G is, for example, a glass preform for an optical fiber core, and the elongated preform divided from the elongated body G1 is used as the optical fiber core by being drawn together with a preform that will become the cladding of the optical fiber.

[0022] 1, the elongation apparatus 1 includes a heating furnace 11, an upper chuck 12, a lower chuck 13, a camera 14, an outer diameter measuring device 15, a control device 16, a relay device 17, and a server (processing device) 18. The control device 16 is connected to the heating furnace 11, the upper chuck 12, the lower chuck 13, the camera 14, the outer diameter measuring device 15, and the relay device 17 so as to be able to communicate with each other.

[0023] The heating furnace 11 has a cylindrical furnace tube 111 and a ring-shaped heater 112. The heater 112 is disposed so as to surround the outer periphery of the furnace tube 111.

[0024] The upper chuck 12 is configured to grip a support rod R1 connected to the upper end of the glass base material G. The upper chuck 12 is provided so as to be movable up and down by a vertical movement mechanism (not shown). When the elongation of the glass base material G starts, the upper chuck 12 moves toward the heating region of the heater 112 of the heating furnace 11 (downward in FIG. 1 ) and feeds the glass base material G into the heating furnace 11.

[0025] The lower chuck 13 is configured to grip a support rod R2 connected to the lower end of the glass preform G. The lower chuck 13 is provided so as to be movable up and down by a vertical movement mechanism (not shown). When the elongation of the glass preform G starts, the lower chuck 13 moves downward at a speed faster than the upper chuck 12, and takes over the elongated body G1 elongated from the glass preform G.

[0026] The camera 14 is configured to capture an image of the elongated body G1 during elongation of the glass preform G, and transmit data of the captured image to the control device 16. The outer diameter measuring device 15 is configured to measure the outer diameter of the elongated body G1 using, for example, a laser beam during elongation of the glass preform G, and transmit the measurement result to the control device 16.

[0027] The control device 16 is configured to control the moving speeds of the upper chuck 12 and the lower chuck 13 so that the measured outer diameter value of the elongated body G1 coincides with the target outer diameter value, based on the measured outer diameter value of the elongated body G1 acquired by the outer diameter measuring device 15. The control device 16 is also configured to control the temperature of the heater 112.

[0028] (Method of stretching glass base material) Next, a method for elongating a glass preform G using the elongation apparatus 1 will be described. First, the upper chuck 12 is moved toward the heating region of the heater 112 of the heating furnace 11, and the glass preform G is fed into the heating furnace 11. Then, when the glass preform G is heated and softened by the heater 112, the lower chuck 13 is moved downward at a speed faster than the upper chuck 12. As a result, as illustrated in FIG. 1 , the softened portion of the glass preform G softened in the heating furnace 11 is elongated downward, and an elongated body G1 is obtained.

[0029] The movement speeds of the upper chuck 12 and the lower chuck 13 are controlled by the control device 16 so that the measured outer diameter value of the elongated body G1 coincides with the target outer diameter value. For example, if the measured outer diameter value of the elongated body G1 is larger than the target outer diameter value, the movement speed of the upper chuck 12 is decreased or the movement speed of the lower chuck 13 is increased so that the outer diameter of the elongated body G1 being elongated becomes smaller.

[0030] (Determine whether there is an abnormality) Server 18 detects external and internal abnormalities in elongated body G1 obtained by elongation device 1. Server 18 includes a processing unit 21 and a storage unit (storage device) 22. Storage unit 22 is, for example, a read-only memory (ROM) or a random access memory (RAM).

[0031] The processing unit 21 is a microprocessor or the like, and reads and executes a computer program including part or all of the processes described below from the storage unit 22. The computer program can be installed from an external server device or the like.

[0032] (a) Abnormality detection based on outer diameter measurement The control device 16 acquires position information of the measurement point of the elongated body G1 measured by the outer diameter measuring device 15 during elongation of the glass preform G. The position information indicates, for example, the distance from a reference position to the measurement point of the outer diameter (hereinafter referred to as "first elongation length"). The reference position is, for example, a position where a marking M is applied to the glass preform G as the elongation start position of the elongated body G1.

[0033] The first extension length is calculated in the control device 16, for example, based on the position information of the lower chuck 13 at the time when the reference position passes the position of the outer diameter measuring device 15 and the position information of the lower chuck 13 at the time of measurement by the outer diameter measuring device 15.

[0034] The control device 16 also acquires the outer diameter measurement value of the elongated body G1 acquired by the outer diameter measuring device 15. Then, the control device 16 transmits to the relay device 17 first data that associates the outer diameter measurement value with the first elongated length.

[0035] When relay device 17 receives the first data from control device 16, it transmits the first data to server 18. When processing unit 21 in server 18 receives the first data transmitted from control device 16 via relay device 17, it stores the first data in storage unit 22.

[0036] The above-described steps of obtaining the outer diameter measurement value, obtaining the positional information indicating the location where the outer diameter is measured, and storing the first data associating the outer diameter measurement value with the first elongation length indicated by the positional information are repeatedly performed during the elongation of the glass base material G.

[0037] After the elongation of the glass preform G is completed, the processing unit 21 determines whether or not there is an abnormal portion, such as a portion where the outer diameter has changed, in the elongated body G1, based on the outer diameter measurement value of the first data stored in the memory unit 22. If the processing unit 21 detects an abnormal portion, it identifies the positions of, for example, a first end and a second end of the abnormal portion based on the first elongation length of the first data, and stores the positions of the first end and the second end in the memory unit 22.

[0038] (b) Abnormality detection based on captured images The control device 16 acquires position information of the image capturing location of the elongated body G1 captured by the camera 14 during elongation of the glass preform G. The position information indicates, for example, the distance from the reference position to the image capturing location (hereinafter referred to as the "second elongation length").

[0039] The second extension length is calculated by the control device 16 based on, for example, position information of the lower chuck 13 at the timing when the reference position passes the position of the camera 14 and position information of the lower chuck 13 at the timing when the image is captured by the camera 14.

[0040] The control device 16 also acquires a captured image of the elongated body G1 captured by the camera 14. The control device 16 then transmits to the relay device 17 second data that associates the captured image with the second elongated length.

[0041] When the relay device 17 receives the second data from the control device 16, it transmits the second data to the server 18. When the processing unit 21 in the server 18 receives the second data transmitted from the control device 16 via the relay device 17, it stores the second data in the storage unit 22.

[0042] The above-described acquisition of captured images, acquisition of positional information indicating the captured location, and storage of second data associating the captured images with the second elongation length indicated by the positional information are repeatedly performed during the elongation of the glass base material G.

[0043] After the elongation of the glass base material G is completed, the processing unit 21 determines whether or not there are any abnormalities such as bubbles or surface scratches in the elongated body G1 based on the captured image of the second data stored in the storage unit 22.

[0044] For example, if a portion of the elongated body G1 has bubbles or surface scratches, the captured image of that portion tends to have a higher average brightness due to light scattering. Therefore, if the average brightness of the captured image of the elongated body G1 exceeds a predetermined threshold, the processing unit 21 can determine that the elongated body G1 has an abnormality. This method makes it possible to automate the detection of abnormalities in the elongated body G1.

[0045] When the processing unit 21 detects an abnormal portion, it identifies, for example, the positions of the first end and the second end of the abnormal portion based on the second extension length of the second data, and stores the positions of the first end and the second end in the memory unit 22.

[0046] 1, when the glass preform G is elongated in the vertical direction, the elongated body G1 is often divided into a plurality of elongated preforms while standing in the vertical direction. In such a case, it is not easy for an operator to check for the presence or absence of abnormalities along the entire length of the elongated body G1 extending in the vertical direction.

[0047] In contrast, in the elongating apparatus 1 according to the embodiment of the present disclosure, as described above, the first data and the second data are stored in the storage unit 22 during the elongation of the glass preform G. After the elongation of the glass preform G, the processing unit 21 determines whether the elongated body G1 is abnormal based on the stored first data and second data. This reduces the burden on the operator.

[0048] The processing unit 21 is not limited to a configuration that performs abnormality determination using each of the first data and the second data, but may be configured to perform abnormality determination using either the first data or the second data.

[0049] (Determining the division position) (a) Description of the task Fig. 2 is a schematic diagram for explaining the problem that occurs when dividing the elongated body G1 shown in Fig. 1. For example, suppose that three elongated base materials G2 each having a fixed length L1 are obtained by dividing the elongated body G1 formed by the elongated device 1.

[0050] In such a case, it is assumed that an abnormal portion 51 is detected in one of the elongated base materials G2 after dividing the elongated body G1, and the lengths of the two portions obtained by removing the abnormal portion 51 from the elongated base material G2 are L3a and L3b, respectively.

[0051] And when the lengths L3a and L3b are less than the minimum required length as the drawn base material G2 (hereinafter referred to as the "minimum length L2") (L3a < L2, L3b < L2), the entire drawn base material G2 will be discarded, resulting in a decrease in yield. The minimum length L2 is, for example, a value shorter than the fixed length L1 and longer than half of the fixed length L1 (L1×1 / 2 < L2 < L1).

[0052] On the other hand, in the drawing device 1 according to the embodiment of the present disclosure, as described above, during the drawing of the glass base material G, the first data indicating the pair of the measured outer diameter value of the drawn body G1 and the first drawing length, and the second data indicating the pair of the captured image of the drawn body G1 and the second drawing length are stored. And based on these data, the detection of the abnormal part 51 in the drawn body G1 is performed. Therefore, the server 18 shown in FIG. 1 can specify the division position of the drawn base material G2 with respect to the normal part obtained by removing the abnormal part 51 of the drawn body G1 before the division of the drawn body G1.

[0053] (b) Method for determining the division position (b-1) Example 1 FIG. 3 is a schematic diagram (part 1) for explaining the division position of the drawn body G1 determined by the server 18 shown in FIG. 1. Specifically, first, the server 18 determines, as the division point P1, the end of the abnormal part 51 of the drawn body G1 that will not be included in the drawn base material G2 after division, among the first end and the second end of the abnormal part 51. Also, when there is no abnormal part 51 in the portion from the division point P1 to the position of the fixed length L1, the server 18 determines this position as the division point P2.

[0054] Also, assume that the remaining part when cutting at the division point P2 (in the example shown in FIG. 3, the part above the division point P2) is a normal part without the abnormal part 51, and the length of this part is longer than the sum of the fixed length L1 and the minimum length L2. In this case, the server 18 determines the position from the division point P2 to the fixed length L1 as the division point P3.

[0055] As a result, from the elongated body G1, a first elongated base material G2a having a length of the fixed length L1, a second elongated base material G2b having a length of the fixed length L1, and a third elongated base material G2c having a length L4 (L2 ≤ L4 < L1) can be obtained. In this way, since the normal part obtained by removing the abnormal part 51 from the elongated body G1 can be effectively utilized, the reduction in the yield can be suppressed.

[0056] (b-2) Example 2 FIG. 4 is a schematic diagram (part 2) for explaining the splitting position of the elongated body G1 determined by the server 18 shown in FIG. 1. In the example described in FIG. 3, the case where the length of the remaining part when cutting at the splitting point P2 is longer than the total value of the fixed length L1 and the minimum length L2 was described. However, there may be a case where the length of the said part is less than the total value of the fixed length L1 and the minimum length L2.

[0057] For example, assume that the length of the said part is less than the total value of the fixed length L1 and the minimum length L2 and is not less than twice the minimum length L2. In this case, the server 18 determines the middle of the said part as the splitting point P3. As a result, from the elongated body G1, a first elongated base material G2a having a length of the fixed length L1, a second elongated base material G2b having a length L5 (L2 ≤ L5 < L1), and a third elongated base material G2c having a length L5 can be obtained.

[0058] (b-3) Example 3 FIG. 5 is a schematic diagram (part 3) for explaining the splitting position of the elongated body G1 determined by the server 18 shown in FIG. 1. As shown in FIG. 5, in the remaining part when cutting at the splitting point P2, there may be an abnormal part 51. In such a case, the server 18, for example, after determining the splitting point P1 and the splitting point P2, determines the end closer to the splitting point P2 among the first end and the second end of the abnormal part 51 as the splitting point P3.

[0059] Then, as shown in FIG. 5, when the length L6 of the portion between the split point P2 and the split point P3 is not less than the minimum length L2 and less than twice the minimum length L2 (L2 ≦ L6 < L2 × 2), the server 18 uses this portion as the second drawn base material G2b. That is, in this case, from the drawn body G1, the first drawn base material G2a having a fixed length L1 and the second drawn base material G2b having a length L6 can be obtained.

[0060] (Flow of operation) (a) Overall flow FIG. 6 is a flowchart showing the flow of operations when the drawn body G1 is drawn by the drawing device 1 shown in FIG. 1 and the splitting position is determined.

[0061] Referring to FIG. 6, first, during the drawing of the drawn body G1 by the drawing device 1, the server 18 acquires the first data in which the outer diameter measurement value of the drawn body G1 is associated with the first drawing length, and the second data in which the captured image of the drawn body G1 is associated with the second drawing length (step S11).

[0062] Then, the server 18 stores the acquired first data and second data (step S12). Until the drawing of the drawn body G1 is completed, the acquisition of the first data and second data (step S11) and the storage of the first data and second data (step S12) are repeated. Then, after the drawing of the drawn body G1 is completed (step S13), the server 18 determines the splitting position for the drawn body G1 (step S14).

[0063] (b) Flow of splitting position determination process FIGS. 7 to 9 are flowcharts showing the flow of the splitting position determination process shown in FIG. 6. Referring to FIGS. 7 to 9, first, the server 18 tentatively determines, as the first drawn base material G2a, the portion from the first end of the drawn body G1 (for example, the lower end portion of the drawn body G1) to the position of the fixed length L1 (step S31). Then, the server 18 checks, by referring to the stored first data and second data, whether or not there is an abnormal portion 51 in the tentatively determined drawn base material G2a (step S32).

[0064] Next, if an abnormal portion 51 exists in the provisionally determined elongated base material G2a ("YES" in step S32), the server 18 determines an end (e.g., an upper end) of the abnormal portion 51 as a division position P (step S33). Then, the server 18 again provisionally determines the portion from the division position P to the position of the standard length L1 as the first elongated base material G2a (step S31).

[0065] On the other hand, if the provisionally determined elongated base material G2a does not have an abnormal portion 51 ("NO" in step S32), the server 18 finally determines the provisionally determined elongated base material G2a. That is, the server 18 determines an end (e.g., an upper end) of the provisionally determined elongated base material G2a as the dividing position P (step S34).

[0066] Next, the server 18 checks whether the length of the remaining portion when the elongated base material G2a is cut is equal to or greater than the minimum length L2 (step S35).

[0067] Then, it is determined that the length of the portion is equal to or greater than the minimum length L2 ("YES" in step S35). In this case, the server 18 confirms whether the length of the portion is equal to or greater than the minimum length L2 and less than twice the minimum length L2, or is equal to or greater than the minimum length L2 and less than the sum of the minimum length L2 and the standard length L1, or is equal to or greater than the sum of the minimum length L2 and the standard length L1 (step S36).

[0068] Then, if the length of the portion is equal to or greater than the minimum length L2 and less than twice the minimum length L2 ("equal to or greater than L2 and less than 2 x L2" in step S36), the server 18 provisionally determines the entire portion as the second elongated base material G2b (step S37).

[0069] Next, the server 18 refers to the stored first data and second data to check whether or not the provisionally determined elongated base material G2b has an abnormal portion 51 (step S38).

[0070] Next, if the provisionally determined elongated base material G2b has an abnormal portion 51 ("YES" in step S38), the server 18 determines an end (e.g., an upper end) of the abnormal portion 51 as a dividing position P (step S39). Then, the server 18 again provisionally determines the entire remaining portion when cut at the dividing position P as a second elongated base material G2a (step S37).

[0071] On the other hand, if the provisionally determined elongated base material G2b does not have an abnormal portion 51 ("NO" in step S38), the server 18 officially determines the provisionally determined elongated base material G2b (step S40). Then, the server 18 notifies an external device that cuts the elongated body G1 of one or more determined division positions, i.e., division positions for obtaining two elongated base materials G2a and G2b from the elongated body G1 (step S41).

[0072] In step S36, the length of the remaining portion when the determined elongated base material G2a is cut is assumed to be at least twice the minimum length L2 and less than the sum of the minimum length L2 and the fixed length L1 (at least 2×L2 and less than L2+L1 in step S36). In this case, the server 18 provisionally determines half of the portion (e.g., the lower half) as the second elongated base material G2b (step S42).

[0073] Next, the server 18 refers to the stored first data and second data to check whether or not the provisionally determined elongated base material G2b has an abnormal portion 51 (step S43).

[0074] Next, if the provisionally determined elongated base material G2b has an abnormal portion 51 ("YES" in step S43), the server 18 determines an end (e.g., an upper end) of the abnormal portion 51 as the division position P (step S44). Then, the server 18 again provisionally determines the entire remaining portion when cut at the division position P as the second elongated base material G2b (step S42).

[0075] On the other hand, if the provisionally determined elongated base material G2b does not have an abnormal portion 51 ("NO" in step S43), the server 18 finally determines the provisionally determined elongated base material G2b (step S45).

[0076] Next, the server 18 provisionally determines the entire remaining portion of the finally determined elongated base material G2b when it is cut as the third elongated base material G2c (step S46).

[0077] Next, the server 18 refers to the stored first data and second data to check whether or not the provisionally determined elongated base material G2c has an abnormal portion 51 (step S47).

[0078] Next, if the provisionally determined elongated base material G2c has an abnormal portion 51 ("YES" in step S47), the server 18 determines an end (e.g., an upper end) of the abnormal portion 51 as the division position P (step S48). Then, the server 18 again provisionally determines the entire remaining portion when cut at the division position P as the third elongated base material G2c (step S46).

[0079] On the other hand, if the provisionally determined elongated base material G2c does not have an abnormal portion 51 ("NO" in step S47), the server 18 officially determines the provisionally determined elongated base material G2c (step S49). Then, the server 18 notifies, for example, the external device described above, of the determined division positions, i.e., the division positions for obtaining three elongated base materials G2a, G2b, and G2c from the elongated body G1 (step S50).

[0080] In step S36, it is assumed that the length of the remaining portion when the finally determined elongated base material G2a is cut is equal to or greater than the sum of the minimum length L2 and the fixed length L1 ("equal to or greater than L2 + L1" in step S36). In this case, the server 18 provisionally determines the portion of the elongated base material G2a from the end (e.g., the upper end) to the position of the fixed length L1 as the second elongated base material G2b (step S51). Then, the server 18 performs the same processes as those in steps S43 to S50 described above.

[0081] In step S35, it is assumed that the length of the remaining portion when the determined elongated base material G2a is cut is less than the minimum length L2 ("NO" in step S35). In this case, the server 18 checks whether the total length of the elongated body G1 is at least twice the minimum length L2 (step S52).

[0082] If the total length of the elongated body G1 is equal to or greater than twice the minimum length L2 ("YES" in step S52), the server 18 cancels the first elongated base material G2a determined in step S34. The server 18 then provisionally determines the portion from the end (e.g., the lower end) of the elongated body G1 to the middle of the elongated body G1 as the first elongated base material G2a (step S53). The server 18 then refers to the stored first data and second data to confirm whether or not an abnormal portion 51 exists in the provisionally determined elongated base material G2a (step S54).

[0083] Next, if an abnormal portion 51 exists in the provisionally determined elongated base material G2a ("YES" in step S54), the server 18 determines an end (e.g., an upper end) of the abnormal portion 51 as a division position P (step S55). Then, the server 18 again provisionally determines the portion from the division position P to a position half the length of the elongated body G1 as the first elongated base material G2a (step S53).

[0084] On the other hand, if the provisionally determined elongated base material G2a does not have an abnormal portion 51 ("NO" in step S54), the server 18 finally determines the provisionally determined elongated base material G2a. That is, the server 18 determines an end (for example, an upper end) of the provisionally determined elongated base material G2a as the dividing position P (step S56). Then, the server 18 performs the processes from step S37 onwards.

[0085] Also, in step S52, it is assumed that the total length of the elongated body G1 is less than twice the minimum length L2 ("NO" in step S52). In this case, the server 18 notifies, for example, the external device described above, of one or more division positions that have been determined up to step S34, i.e., division positions for obtaining one elongated base material G2a from the elongated body G1 (step S57).

[0086] The external device that has received notification of one or more division positions P from the server 18 divides the elongated body G1 into one or more elongated base materials G2, for example, based on the notified one or more division positions P.

[0087] According to the above-described process for determining the division position, the amount of elongated base material G2 having the standard length L1 can be maximized while appropriately switching from obtaining an elongated base material G2 having the standard length L1 to obtaining an elongated base material G2 having a length greater than the minimum length L2 but less than the standard length L1 depending on the length of the normal part of the elongated body G1, thereby reducing the amount of elongated body G1 and elongated base material G2 that is discarded.

[0088] In the above-described embodiment, the server 18 acquires the first data and the second data, and determines whether the elongated body G1 has an abnormality and determines the division positions of the elongated body G1 based on the acquired data. However, the configuration is not limited to this, and the elongating device 1 may be configured such that, for example, the control device 16 performs part or all of the processes of determining whether the elongated body G1 has an abnormality and determining the division positions of the elongated body G1.

[0089] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. Furthermore, the number, position, shape, etc. of the components described above are not limited to the above embodiments, and can be changed to any number, position, shape, etc. that is suitable for implementing the present invention. [Explanation of symbols]

[0090] 1 Stretching device 11 Heating furnace 12 Upper chuck 13 Lower chuck 14 Camera 15 Outer diameter measuring device 16 Control device 17 Relay Device 18 Server (processing device) 21 Processing section 22 Storage unit (storage device) 51 Abnormal part 111 Furnace tube 112 Heater G1 stretched body G2,G2a,G2b,G2c Stretched base material L1 Standard length L2 minimum length L3, L4, L5, L6 length P1,P2,P3 dividing point R1, R2 support rod

Claims

1. A method for elongating a glass preform, in which a glass preform is elongated while being heated in a heating furnace to form an elongated body from which a plurality of elongated preforms are obtained, comprising the steps of: measuring an outer diameter of the elongated body during elongation of the glass preform, and controlling the measured outer diameter to match a target outer diameter value; acquiring at least one of the outer diameter measurement value and an image of the elongated body in association with a longitudinal position of the elongated body during elongation of the glass preform; performing an abnormality determination step of determining whether or not there is an abnormal portion in the elongated body based on at least one of the outer diameter measurement value and the captured image associated with the longitudinal position of the elongated body; After the elongation of the glass preform is completed, determining division positions for dividing the elongated body into a plurality of the elongated preforms based on the result of the abnormality determination; A method for elongating a glass base material, comprising:

2. At least one of the outer diameter measurement value and the captured image associated with the longitudinal position of the elongated body is stored in a storage device; In the step of determining an abnormality, the abnormality determination is performed based on at least one of the outer diameter measurement value and the captured image stored in the storage device. The method for elongating a glass base material according to claim 1 .

3. When the abnormality determination is performed based on the captured image, The method for elongating a glass base material according to claim 2 , wherein the elongated body is determined to have an abnormality when an average brightness of the captured image exceeds a predetermined threshold value.

4. In the step of determining the division position, 4. A method for elongating a glass base material according to claim 1, wherein when the elongated base material is cut to a predetermined length from a first end of a normal portion excluding an abnormal portion of the elongated body, if the remaining length after cutting is equal to or greater than the minimum length of the elongated base material, the position at the predetermined length from the first end is determined as the division position, and if the remaining length after cutting is less than the minimum length of the elongated base material, the middle of the normal portion is determined as the division position.

5. A glass preform elongation apparatus for forming an elongated body in which a plurality of elongated preforms are obtained by elongating a glass preform while heating it in a heating furnace, comprising: a control device that measures the outer diameter of the elongated body during elongation of the glass base material and controls the measured outer diameter to match a target outer diameter value; a processing device that acquires at least one of the outer diameter measurement value and an image of the elongated body in association with a longitudinal position of the elongated body during elongation of the glass base material, The processing device includes: performing an abnormality determination to determine whether or not there is an abnormal portion in the elongated body based on at least one of the outer diameter measurement value and the captured image associated with the longitudinal position of the elongated body; After the elongation of the glass preform is completed, dividing positions for dividing the elongated body into the plurality of elongated preforms are determined based on the result of the abnormality determination. Glass base material elongation device.

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