Quartz glass rod and method for manufacturing the same
By implementing stepwise elongation and localized heating during drawing to correct bends, the method addresses distortion in quartz glass rods, enhancing productivity and minimizing cracking risks.
Patent Information
- Application Number
- JP2024038138
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-12
- Publication Date
- 2025-09-26
AI Technical Summary
Existing manufacturing processes for quartz glass rods suffer from distortion due to heating and cutting, leading to potential cracking during shipping, necessitating a strain removal process that reduces productivity.
A method involving stepwise elongation and localized heating with a burner flame during multiple drawing processes to correct bends, ensuring distortion is confined to the ends and minimized in the middle, thereby omitting the strain removal step.
Enhances productivity by eliminating the strain removal process while reducing the risk of cracks, primarily at the ends where distortion is greater, thus maintaining product integrity.
Smart Images
Figure 2025139291000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a quartz glass rod obtained by elongating a glass base material to a predetermined outer diameter using a glass processing lathe equipped with a burner (hereinafter referred to as a glass lathe), and a method for producing the same. [Background technology]
[0002] In the process of manufacturing a quartz glass rod by heating a glass base material with a burner flame on a glass lathe, distortion occurs at multiple locations in the manufactured quartz glass rod due to heating by the burner flame.
[0003] Figures 1 and 2 show the form of distortion that occurs in a quartz glass rod 1. When the quartz glass rod is removed from the glass lathe after it has been drawn, both ends are cut with a burner flame to a specified length, and the product portion is removed. The distortion that occurs at both ends due to the burner flame during this cutting is distortion due to cutting 2. Figure 1 shows a schematic diagram of a quartz glass rod in which distortion due to cutting 2 remains at both ends.
[0004] Figure 2 shows a schematic diagram of a quartz glass rod with distortion 2 due to fusing at both ends, as in Figure 1, and distortion 3 due to bending correction in the middle. The "amount of bending" is sometimes specified as a dimensional tolerance for the quartz glass rod, and if the amount of bending is outside the specification after the drawn-out process to achieve the specified outer diameter, the quartz glass rod is locally softened with a burner flame to correct the bending. During this bending correction, distortion 3 due to bending correction occurs at the position heated by the burner flame. The position and number of bending correction distortions 3 that occur when bending is corrected differ for each quartz glass rod depending on the shape of the bend.
[0005] If localized distortion remains in the quartz glass rod as shown in Figures 1 and 2, it may crack due to vibration or temperature changes after shipping. Conventionally, in order to prevent cracks due to distortion, a process to remove the localized distortion was added at the end of the manufacturing process of the quartz glass rod. Known methods for removing distortion include heating with a burner flame on a glass lathe while moving the burner sequentially from one end to the other, and using an annealing furnace.
[0006] One way to simplify the manufacturing process of quartz glass rods and improve productivity is to omit the strain removal process. However, in this case, the rods will be shipped with localized strain remaining, which means there is still a risk of them breaking after shipping, as mentioned above. Summary of the Invention [Problem to be solved by the invention]
[0007] The present invention has been made in view of the above problems, and aims to improve productivity by omitting the strain removal step in the manufacturing process of quartz glass rods, and to provide a method of leaving strain that will cause no substantial damage if the resulting residual strain causes a crack in the quartz glass rod after shipment. [Means for solving the problem]
[0008] In order to solve the above problems, a method for producing a quartz glass rod according to one embodiment of the present invention involves drawing a quartz glass rod stepwise through multiple drawing processes to obtain a quartz glass rod of a predetermined diameter. This method for producing a quartz glass rod is characterized in that, during the multiple drawing processes, one or more locations of the quartz glass rod drawn on a glass processing lathe are heated with a burner flame to soften the rod and correct the bend so that the amount of bend falls within a specified range.
[0009] In this way, the distortion that occurs in the middle of the quartz glass rod due to the bending correction is removed by the subsequent elongation process, and distortion remains only at both ends, which reduces the possibility of cracks occurring in the middle part after shipping.
[0010] In the present invention, the bending correction is preferably performed immediately before the final stretching of the multiple stretching processes, thereby minimizing the number of stretching processes after bending correction and suppressing deterioration of the amount of bending.
[0011] In another embodiment of the present invention, a method for manufacturing a quartz glass rod involves stepwise elongating a quartz glass rod through multiple elongation processes to obtain a quartz glass rod of a predetermined diameter. This method for manufacturing a quartz glass rod is characterized in that, after the final elongation process of the multiple elongation processes, one or more locations of the quartz glass rod elongated on a glass processing lathe are heated with a burner flame to soften and straighten the quartz glass rod so that the amount of bending falls within a specified range. The amount of heat used for straightening is adjusted so that the strain generated in the middle portion of the quartz glass rod due to straightening is smaller than the strain generated at both ends of the quartz glass rod when the quartz glass rod is fused. It is preferable that the amount of heat used for straightening is smaller than the amount of heat used when fusion-cutting the quartz glass rod.
[0012] In this way, if cracks occur after shipping, they are more likely to occur at both ends where the distortion is greater, and the possibility of cracks occurring at the position of distortion caused by bending correction in the middle portion can be kept extremely low.
[0013] Furthermore, the quartz glass rod according to an embodiment of the present invention is a quartz glass rod obtained by elongating a glass base material to a predetermined outer diameter using a glass processing lathe, and is characterized in that it has distortion only at both ends.
[0014] In addition, a quartz glass rod according to another embodiment of the present invention is a quartz glass rod obtained by elongating a glass base material to a predetermined outer diameter using a glass processing lathe, characterized in that the rod has multiple strains at both ends and in the intermediate portion, and the strain at one or more locations in the intermediate portion is smaller than the strain at both ends. [Effects of the Invention]
[0015] The elimination of the strain removal process from the manufacturing process of quartz glass rods improves productivity of quartz glass rods. On the other hand, damage caused by cracks due to residual strain in the product can be avoided or significantly reduced by changing how the strain is left. [Brief explanation of the drawings]
[0016] [Figure 1] FIG. 1 is a diagram schematically showing a quartz glass rod in which distortion 2 caused by fusing remains at both ends. [Figure 2] FIG. 1 is a diagram showing a quartz glass rod having distortion 2 due to fusing at both ends and distortion 3 due to bending correction in the middle portion. [Figure 3] FIG. 10 is a diagram showing how distortion 3 caused by bending correction performed during stepwise stretching is removed by subsequent stretching. DETAILED DESCRIPTION OF THE INVENTION
[0017] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these.
[0018] Figure 1 shows a schematic diagram of a quartz glass rod in which distortion 2 due to fusing remains at both ends. In the case of the distortion shown in Figure 1, only distortion 2 due to fusing occurs. The location where distortion 2 due to fusing occurs is within the range defined as a non-product area, where the outer diameter has changed due to fusing. Even if cracks occur in the distorted areas at both ends, this will only damage the non-product area, and no substantial damage will occur. Therefore, in a quartz glass rod in which distortion has occurred only at both ends, as in this case, it is possible to omit the distortion removal process and conclude the manufacturing process with distortion remaining at both ends, without causing any problems when shipping.
[0019] On the other hand, Figure 2 shows a schematic diagram of a quartz glass rod in which distortion 2 due to fusing remains at both ends, as in Figure 1, and distortion 3 due to bending correction also remains in the middle part. In the case of distortion as shown in Figure 2, distortion 3 due to bending correction occurs in the product part (middle part) of the quartz glass rod, so if the distortion removal process is omitted when the rod is shipped, the product part may break and cause damage.
[0020] Therefore, in this embodiment, as a processing method that does not leave distortion 3 due to bending correction even if the distortion removal step is omitted, bending correction is performed during multiple elongation processes.
[0021] Typically, straightening is performed after the drawing to the specified outer diameter is completed to prevent the amount of bending from worsening again after correction. The drawing process is often performed in two or more stages depending on the difference between the outer diameter of the glass base material and the specified outer diameter, as well as the required outer diameter variation accuracy. For example, if the glass base material before drawing is φ100 mm in diameter and the specified outer diameter of the quartz glass rod to be manufactured is φ60 mm, the processing procedure is to process it to a diameter of φ65 mm in the first drawing, and then finish it to the specified diameter of φ60 mm in the second drawing. Normally, straightening is performed after drawing to the specified diameter of φ60 mm is completed, and the amount of bending is within the specified range. With this procedure, if a distortion removal process is not performed after the bending correction is completed, distortion caused by the straightening will remain in the product part (middle part) of the quartz glass rod.
[0022] In contrast, in this embodiment, when finishing to the specified outer diameter by two-stage drawing, the bending correction is performed between the first and second drawing. As a result, any distortion in the product due to the bending correction is removed by heating with a burner flame during the second drawing process. In other words, the second drawing process serves as both a drawing process and a distortion removal process. Therefore, by performing the bending correction in this order, it is possible to avoid distortion remaining in the product due to the bending correction, even without performing a distortion removal process after the drawing is completed.
[0023] Figure 3 shows how distortion 3 caused by bending correction performed during stepwise drawing is removed by subsequent drawing. Drawing using a glass lathe is a process in which a burner 6 is moved from one end to the other while simultaneously moving the lathe chuck 5 holding the quartz glass rod 1 in the opposite direction to the burner 6, thereby gradually forming the quartz glass in the heated area to the target outer diameter. Distortion that occurs in one or more places in the product part of the quartz glass rod due to bending correction is completely removed by heating with the burner flame during drawing (reference number 4 in Figure 3).
[0024] If stretching is performed after bending correction, the corrected bending amount may worsen with subsequent stretching. Therefore, it is preferable to perform bending correction during stepwise stretching before the final stretching. For example, if stretching is performed in three steps, bending correction is performed after the second stretching is completed, and the only stretching performed after bending correction is the third stretching to finish the specified outer diameter, thereby minimizing the deterioration of the bending amount.
[0025] Even if the bending is corrected before the final stretching, it is not possible to completely eliminate the worsening of the bending amount due to the final stretching, so it is necessary to correct the bending in anticipation of the amount of bending that will worsen with subsequent stretching. Therefore, it is necessary to correct the bending amount to a smaller amount than in the normal procedure of correcting the bending after the stretching is completed. In cases where the required accuracy of the amount of bending is strict, this procedure may be difficult to achieve.
[0026] To comply with strict regulations regarding the amount of bending, the bending is corrected after the stretching is complete, as in the past. However, the bending is corrected under processing conditions that ensure that the distortion caused by the bending correction is smaller than the distortion caused by fusing at both ends. This significantly reduces the risk of the product cracking due to distortion caused by the bending correction after shipping.
[0027] The burner gas flow rate and heating time during bend correction are adjusted, and the burner heating conditions are set so that the amount of heat applied during bend correction is sufficiently smaller than the amount of heat applied when fusing both ends. If the distortion removal process after bend correction is omitted, distortion caused by bend correction will remain in the product, but by adjusting the amount of heat applied by the burner as described above, this distortion will be sufficiently smaller than the distortion caused by fusing both ends. If cracks occur after shipping with this type of distortion, they are more likely to occur at the locations where the distortion caused by fusing the ends, where the distortion is greater, and the shape of the product can also be kept extremely low.
[0028] The magnitude of the distortion remaining in the quartz glass rod can be estimated from the heating conditions using the burner, but by using a polarized light distortion detector, it is possible to easily determine the degree of distortion caused by fusing and the degree of distortion caused by bending correction.
[0029] As methods for avoiding cracking of the product part due to residual distortion caused by bending correction while omitting the distortion removal process to improve the productivity of quartz glass rods, we have explained two methods: "a method of correcting bending during the stepwise drawing process and removing distortion in the product part due to bending correction in the drawing after the correction" and "a method of reducing the risk of cracking of the product part due to distortion caused by the amount of bending by making the distortion caused by the amount of bending smaller than the distortion caused by fusing at both ends."Which of these two methods should be adopted should be selected taking into consideration several factors, such as the amount of damage if the product part breaks and the required accuracy of the amount of bending.
[0030] Although the embodiments of the present invention have been described above, the embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]
[0031] 1 quartz glass rod 2 Distortion due to fusing 3 Distortion due to bending correction 4 Strain due to bending correction eliminated by stretching 5 lathe chuck 6 Lathe Burner
Claims
1. A method for producing a quartz glass rod by stepwise elongating the quartz glass rod through a plurality of elongation processes to obtain a quartz glass rod of a predetermined diameter, comprising: A method for manufacturing a quartz glass rod, characterized in that, during the multiple elongation processes, one or more locations of the quartz glass rod elongated on a glass processing lathe are heated with a burner flame to soften it and correct the bending amount so that it falls within a specified range.
2. 2. The method for producing a quartz glass rod according to claim 1, wherein the bending correction is carried out immediately before the final elongation process among the multiple elongation processes.
3. A method for producing a quartz glass rod by stepwise elongating the quartz glass rod through a plurality of elongation processes to obtain a quartz glass rod of a predetermined diameter, comprising: After the final elongation process of the multiple elongation processes, one or more locations of the quartz glass rod elongated by the glass processing lathe are heated with a burner flame to soften the rod and correct the bending amount so that it falls within a specified range; A method for manufacturing a quartz glass rod, characterized in that the amount of heat used in the bend correction is adjusted so that the distortion generated in the middle part of the quartz glass rod due to the bend correction is smaller than the distortion generated at both ends of the quartz glass rod when the quartz glass rod is melted.
4. 4. The method for manufacturing a quartz glass rod according to claim 3, wherein the amount of heat used in correcting the bend is smaller than the amount of heat used in fusing the quartz glass rod.
5. A quartz glass rod produced by drawing a glass base material to a predetermined outer diameter using a glass processing lathe, which has distortion only at both ends.
6. A quartz glass rod is obtained by elongating a glass base material to a predetermined outer diameter using a glass processing lathe, and is characterized in that the quartz glass rod has a plurality of distortions at both ends and in an intermediate portion, and one or more distortions in the intermediate portion are smaller than the distortions at both ends.