Full-sealing device for small-size preform

Abstract

The invention provides a full-sealing device for a small-size preform, which is characterized in that the full-sealing device comprises a tail rod sealing device, a quartz sealing cylinder and a quartz sealing cylinder fixing base which are hermetically connected in sequence from top to bottom, and the quartz sealing cylinder fixing base is fixed at the upper end of an upper furnace mouth of a wire drawing furnace; a gap is formed between the quartz sealing cylinder and the optical fiber preform to form a non-contact sealing structure. Due to the adoption of a full-sealing mode, the whole preform can be sealed, the sealed cavity covers a gap between the preform and a heating element in the drawing furnace and a gap between the preform and a quartz sealing cylinder, and the volume of the sealed cavity is far greater than the size of a cavity of a conventional sealing device, so that even if the sealing is too tight, the sealing effect is good. As the volume of the sealed cavity is obviously increased, the furnace pressure in the whole sealed cavity is not too high, and the attenuation performance of the optical fiber is not influenced.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber production, and in particular to a fully sealed device for a small-size preform rod. Background Art

[0002] Generally, optical fiber is made by heating and softening the optical fiber preform rod in the drawing furnace. The drawing furnace is a very critical functional equipment for optical fiber drawing. When manufacturing optical fiber, the temperature in the drawing furnace reaches about 2000 degrees Celsius. The heating element in the drawing furnace is generally made of graphite. In order to protect the graphite heating element material in the drawing furnace, it is necessary to maintain an inert gas atmosphere inside the drawing furnace. Usually, a mixed gas of argon and helium is introduced as a protective gas, and the external air flowing into the drawing furnace needs to be controlled. In order to prevent air from entering the drawing furnace during the drawing process of the optical fiber preform rod, a sealing device needs to be placed at the mouth of the drawing furnace.

[0003] The sealing device plays a very important role in the wire drawing process. If the mouth of the wire drawing furnace is sealed too tightly or not tightly, it will seriously affect the performance of the optical fiber. Usually, the sealing device is placed on the mouth of the wire drawing furnace to seal the preform rod. The sealed cavity is only the gap between the preform rod and the heating element inside the wire drawing furnace. Its volume is small. If the seal is too tight, as the inert protective gas continues to flow into the drawing furnace, the furnace pressure in the wire drawing furnace gradually increases. Excessive pressure in the furnace will cause impurities in the wire drawing furnace to diffuse into the optical fiber, thereby affecting the attenuation performance of the optical fiber. If the seal is not tight, the airflow in the wire drawing furnace will be disturbed. Due to the turbulence of the airflow and the change of the pressure in the furnace, the temperature distribution in the wire drawing furnace will be uneven, which will not only cause fluctuations in the diameter of the optical fiber, but also cause fluctuations in the non-roundness of the optical fiber cladding, and ultimately cause important indicators such as the optical fiber cladding diameter and cladding non-roundness to be scrapped. If the seal is not tight and cannot be dealt with in time, outside air will continue to enter the drawing furnace, and the graphite heating element material in the drawing furnace will be oxidized, which will seriously affect its service life and the strength of the optical fiber, resulting in the adverse consequence of double damage to the optical fiber product and processing equipment.

[0004] For small-sized optical fiber preforms with uniform outer diameter, a non-contact air curtain sealing method is generally used. This method uses inert protective gas to be ejected at high speed from the outlet of the sealing device to form an air curtain, thereby isolating the inside of the drawing furnace from the outside air to achieve a sealing effect. The sealing device has a simple structure and a long service life, and is suitable for preforms with uniform diameters. However, its air seal has poor stability. If the axis position of the preform deviates significantly during the drawing process, the gap between one side of the preform and the sealing device will be too large, resulting in disorder and fluctuation of the gas field and thermal field in the drawing furnace, which in turn causes problems such as fluctuation of the optical fiber diameter and oxidation of the graphite heating material. Summary of the invention

[0005] The object of the present invention is to provide a fully sealed device for small-size preform rods which is beneficial to improving the process stability of optical fiber production.

[0006] The present invention is achieved in that: The present invention provides a fully sealed device for a small-size preform rod, which is characterized by comprising a tail rod sealing device, a quartz sealing tube and a quartz sealing tube fixing base which are sealed and connected in sequence from top to bottom, wherein the quartz sealing tube fixing base is fixed to the upper end of the upper furnace mouth of a drawing furnace, and a gap is provided between the quartz sealing tube and the optical fiber preform rod to form a non-contact sealing structure.

[0007] According to the above technical scheme, the quartz sealing tube includes at least two sections of quartz sealing tubes from bottom to top, and the structure of each section of quartz sealing tube is the same. The upper end of each section of quartz sealing tube is provided with a groove, and the lower end is internally convex downward. The grooves and convexities of the two adjacent sections of the quartz sealing tube are sealed to form a sealing structure consistent with the inner diameter and outer diameter of the middle part of the quartz sealing tube. The lowermost quartz sealing tube is sealed with a quartz sealing tube fixed base, and the uppermost quartz sealing tube is sealed with a tail rod sealing device.

[0008] According to the above technical solution, the tail rod sealing device includes a tail rod glass sealing ring installed in the groove of the uppermost quartz sealing tube, and a flexible sealing member is arranged in the tail rod glass sealing ring. The flexible sealing member is pressed by a sealing quartz pressure ring arranged at its upper end, and the flexible sealing member contacts the tail rod of the optical fiber preform rod to form a contact sealing connection.

[0009] According to the above technical solution, a groove for installing a flexible seal is provided at the upper end of the tail rod glass sealing ring, the depth of the groove is 3-10 mm, and the outer diameter of the groove is 40-60 mm larger than the inner diameter of the tail rod glass sealing ring.

[0010] According to the above technical solution, the inner diameter and outer diameter of each section of the quartz sealing tube are the same.

[0011] According to the above technical solution, the quartz sealing tube fixing base is provided with a groove which matches with the protrusion at the lower end of the quartz sealing tube.

[0012] According to the above technical solution, the heights of the various sections of the quartz sealing tube are the same, the height of each section of the quartz sealing tube is 200-400 mm, and the inner diameter of each section of the quartz sealing tube is 15-40 mm larger than the diameter of the uniform preform rod.

[0013] According to the above technical solution, the inner diameter of the tail rod glass sealing ring is 4~10mm larger than the outer diameter of the tail rod, the height of the tail rod glass sealing ring is 20~40mm, and the outer diameter of the tail rod glass sealing ring is 4~8mm smaller than the inner diameter of the groove at the upper end of the quartz sealing tube.

[0014] According to the above technical solution, the flexible sealing member is a sealing soft felt that matches the tail rod, the inner diameter of the sealing soft felt is 2~5mm smaller than the outer diameter of the tail rod, the inner wall of the quartz soft felt has a cutout, the cutout length is 1~3mm, the number of cutouts is 16~32, and the outer diameter of the sealing soft felt is 4~8mm smaller than the outer diameter of the tail rod or the tail tube glass sealing ring groove.

[0015] According to the above technical solution, the inner diameter of the sealing quartz pressure ring is 4-10 mm larger than the outer diameter of the tail rod, the height of the sealing quartz pressure ring is 40-60 mm, and the outer diameter of the sealing quartz pressure ring is 4-8 mm smaller than the inner diameter of the groove at the upper end of the quartz sealing tube. The beneficial effects of the present invention are: 1. The present invention forms a non-contact sealing structure by placing a fully sealed quartz cylinder at the upper furnace mouth of the heating cavity of the drawing furnace. Since the present invention adopts a fully sealed method, the entire preform can be sealed. The sealed cavity covers the gap between the preform and the heating element in the drawing furnace and the gap between the preform and the quartz sealing cylinder. The volume of the sealed cavity is much larger than the cavity size of the conventional sealing device. For this reason, even if the seal is too tight, the furnace pressure in the entire sealed cavity will not be too high, given that the volume of the sealed cavity has increased significantly, and thus will not affect the attenuation performance of the optical fiber.

[0016] 2. Since the tail rod sealing device is configured, and since the diameter of the tail rod is significantly smaller than that of the preform rod, the sealing area of ​​the tail rod is much smaller than that of the preform rod, so the sealing difficulty of the tail rod is much lower than that of the preform rod. In addition, the sealing device for the tail rod of the present invention is a flexible seal with the tail rod during the wire drawing process, and the sealing device can always fit tightly with the tail rod as the position of the tail rod changes, and there will be no loose sealing, thereby ensuring the tightness of the seal. Good sealing ensures the stability of the air flow field and thermal field in the furnace.

[0017] 3. The present invention uses multiple sections of quartz sealing tubes with the same structure to make the quartz sealing tubes more compatible and applicable to optical fiber preforms of different sizes, thus avoiding the need to replace flexible seals of different sizes due to different sizes of optical fiber preforms during production, reducing the number of flexible seals and lowering the optical fiber manufacturing cost.

[0018] 4. The present invention adopts a fully sealed sealing method with good sealing effect, which prolongs the service life of the graphite heating element in the drawing furnace, improves the quality of the optical fiber, and can effectively reduce the manufacturing cost of the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A schematic structural diagram of a fully sealed device for a small-sized preform provided in an embodiment of the present invention.

[0020] Figure 2 A schematic diagram of tail rod sealing provided in an embodiment of the present invention.

[0021] Figure 3 A schematic diagram of the soft sealing felt structure of a tail rod provided in an embodiment of the present invention.

[0022] Among them, 1. optical fiber; 2. optical fiber drawing furnace; 3. optical fiber preform rod; 4. quartz sealing tube fixing base; 5. first section quartz sealing tube; 6. second section quartz sealing tube; 7. third section quartz sealing tube; 8. tail rod glass sealing ring; 9. flexible sealing element; 10. sealing quartz pressure ring; 11. tail rod. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the product of the application is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0027] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0030] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0031] The embodiment of the present invention discloses a fully sealed device for a small-sized optical fiber preform, which is fixed to the upper furnace port of an optical fiber drawing furnace 2 and is used to protect the graphite heating element in the drawing furnace from being oxidized during the drawing process of the small-sized optical fiber preform, and to form a stable airflow field and temperature field in the optical fiber drawing furnace. Figure 1As shown, it comprises a tail rod sealing device, a quartz sealing cylinder and a quartz sealing cylinder fixing base 4 which are sealed and connected in sequence from top to bottom, the quartz sealing cylinder fixing base 4 is fixed to the upper end of the upper furnace opening of the drawing furnace 2, and a gap is provided between the quartz sealing cylinder and the optical fiber preform 3 to form a non-contact sealing structure. The present invention forms a non-contact sealing structure by placing a fully sealed quartz cylinder at the furnace opening at the upper end of the heating cavity of the drawing furnace, thereby avoiding the problem of air flow field and thermal field disorder in the drawing furnace caused by the axial position deviation of the optical fiber preform during the drawing process, and improving the process stability of optical fiber production.

[0032] In this embodiment, the quartz sealing cylinder includes three sections of quartz sealing cylinders from bottom to top, namely, the first section of quartz sealing cylinder 5, the second section of quartz sealing cylinder 6 and the third section of quartz sealing cylinder 7, and each section of quartz sealing cylinder has the same structure. The upper end of each section of quartz sealing cylinder is provided with a groove, and the lower end is convex downward inside, and the grooves and convexities of the adjacent two sections of quartz sealing cylinders are sealed to form a sealing structure consistent with the inner diameter and outer diameter of the middle part of the quartz sealing cylinder. The quartz sealing cylinder 5 at the lower end is sealed with the quartz sealing cylinder fixed base 4, and the quartz sealing cylinder fixed base is provided with a groove that matches the convexity at the lower end of the quartz sealing cylinder, and the quartz sealing cylinder 7 at the upper end is sealed with the tail rod sealing device.

[0033] Specifically, the inner diameters of the first section quartz sealing tube 5, the second section quartz sealing tube 6 and the third section quartz sealing tube 7 are the same, and the outer diameters of the first section quartz sealing tube 5, the second section quartz sealing tube 6 and the third section quartz sealing tube 7 are the same. The heights of the first section quartz sealing tube 5, the second section quartz sealing tube 6 and the third section quartz sealing tube 7 are the same, and the height of the quartz sealing tube is 200-400 mm. The inner diameter of each section of the quartz sealing tube (5, 6, 7) is 15-40 mm larger than the diameter of the uniform preform rod 3.

[0034] Preferably, the height of the groove at the upper end of each section of the quartz sealing tube (5, 6, 7) is 20-50 mm, and the inner diameter of the groove is 10-15 mm larger than the inner diameter of the quartz sealing tube.

[0035] Preferably, the height of the protrusion at the lower end of each section of the quartz sealing tube (5, 6, 7) is 20-50 mm, and the outer diameter of the protrusion is 10-15 mm smaller than the outer diameter of the quartz sealing tube.

[0036] In this embodiment, the tail rod sealing device includes a tail rod glass sealing ring 8 installed in the groove of the uppermost quartz sealing tube, a flexible sealing member 9 is arranged in the tail rod glass sealing ring 8, the flexible sealing member 9 is pressed by a sealing quartz pressure ring 10 arranged at the upper end thereof, and the flexible sealing member 8 contacts the tail rod of the optical fiber preform rod to form a flexible contact sealing connection. The upper end of the tail rod glass sealing ring 8 is provided with a groove for installing the flexible sealing member.

[0037] like Figure 2 As shown, the inner diameter of the tail rod glass sealing ring 8 is 4-10 mm larger than the outer diameter of the tail rod 11, the height of the glass sealing ring 8 is 20-40 mm, and the outer diameter of the glass sealing ring 8 is 4-8 mm smaller than the inner diameter of the groove at the upper end of the quartz sealing tube 7. The depth of the groove set on the glass sealing ring 8 is 3-10 mm, and the outer diameter of the groove is 40-60 mm larger than the inner diameter of the glass sealing ring 8. Figure 3 As shown, the flexible sealing member 9 is a sealing felt that matches the tail rod, the inner diameter of the sealing felt 9 is 2-5 mm smaller than the outer diameter of the tail rod 11, the inner wall of the sealing felt 9 has a cutout, the cutout length is 1-3 mm, the number of cutouts is 16-32, and the outer diameter of the sealing felt 9 is 4-8 mm smaller than the outer diameter of the groove of the tail rod or tail tube glass sealing ring 8. Figure 2 As shown, the inner diameter of the sealing quartz pressure ring 10 is 4-10 mm larger than the outer diameter of the tail rod 11, the height of the sealing quartz pressure ring 10 is 40-60 mm, and the outer diameter of the sealing quartz pressure ring 10 is 4-8 mm smaller than the inner diameter of the groove at the upper end of the quartz sealing tube 7. The tail rod sealing device on the tail rod can move along with the movement of the position of the tail rod, and the sealing device is always close to the tail rod, thereby ensuring the tightness of the seal, and good sealing ensures the stability of the air flow field and thermal field in the furnace.

[0038] In addition, the tail rod in this embodiment can also be replaced by a tail pipe, and the specific name can be determined according to actual working conditions.

[0039] The production process of the device of the present invention comprises the following steps: First, install the tail rod glass sealing ring 8, sealing soft felt 9 and sealing quartz pressure ring 10 on the tail rod 11 of the optical fiber preform rod in sequence. Then hang the optical fiber preform rod 3 on the feeding mechanism of the drawing tower, and then install the quartz sealing cylinders (5, 6, 7) in sequence on the upper furnace mouth of the optical fiber drawing furnace, and slowly put the optical fiber preform rod into the optical fiber drawing furnace 2 until the cone tip of the optical fiber preform rod enters the central position of the heating element of the optical fiber drawing furnace, and the sealing device on the tail rod falls into the groove of the quartz sealing cylinder, completing the assembly process of the full sealing device. During the drawing process, the optical fiber drawing furnace and the sealing cylinder are filled with inert gas until the drawing is completed.

[0040] Since the present invention adopts a fully sealed method, the entire preform can be sealed. The sealed cavity covers the gap between the preform and the heating element in the drawing furnace and the gap between the preform and the quartz sealing tube. The volume of the sealed cavity is much larger than the cavity size of the conventional sealing device. For this reason, even if the seal is too tight, the furnace pressure in the entire sealed cavity will not be too high, given that the volume of the sealed cavity has increased significantly, and thus will not affect the attenuation performance of the optical fiber. And since the tail rod is equipped with a tail rod sealing device, since the diameter of the tail rod is significantly smaller than that of the preform, the sealing area of ​​the tail rod is much smaller than that of the preform, so the sealing difficulty for the tail rod is much lower than that of the preform. In addition, the sealing device for the tail rod of the present invention is a flexible seal with the tail rod during the drawing process, and the sealing device can always fit closely with the tail rod as the position of the tail rod changes, and there will be no loose sealing, thereby ensuring the tightness of the seal, and good sealing ensures the stability of the airflow field and thermal field in the furnace. Based on the above reasons, the present sealing device can avoid the problems caused by the above-mentioned tight sealing and loose sealing.

[0041] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A fully sealed device for small-size preform, characterized in that: It comprises a tail rod sealing device, a quartz sealing tube and a quartz sealing tube fixing base which are sealed and connected in sequence from top to bottom. The quartz sealing tube fixing base is fixed to the upper end of the upper furnace mouth of the drawing furnace. A gap is provided between the quartz sealing tube and the optical fiber preform rod to form a non-contact sealing structure.

2. The fully sealed device for small-size preform according to claim 1, characterized in that: The quartz sealing tube includes at least two sections of quartz sealing tubes, each section of the quartz sealing tube has the same structure, the upper end of each section of the quartz sealing tube is provided with a groove, and the lower end is internally convex downward, the grooves and convexities of the two adjacent sections of the quartz sealing tubes are sealed to form a sealing structure consistent with the inner diameter and outer diameter of the middle part of the quartz sealing tube, the lowermost quartz sealing tube is sealed with a quartz sealing tube fixed base, and the uppermost quartz sealing tube is sealed with a tail rod sealing device.

3. The fully sealed device for small-size preform according to claim 2, characterized in that: The tail rod sealing device comprises a tail rod glass sealing ring arranged in the groove of the uppermost quartz sealing tube, a flexible sealing member is arranged in the tail rod glass sealing ring, the flexible sealing member is pressed by a sealing quartz pressure ring arranged at the upper end thereof, and the flexible sealing member contacts the tail rod of the optical fiber preform rod to form a contact sealing connection.

4. The fully sealed device for small-size preform according to claim 3, characterized in that: The upper end of the tail rod glass sealing ring is provided with a groove for installing a flexible sealing member, the depth of the groove is 3-10 mm, and the outer diameter of the groove is 40-60 mm larger than the inner diameter of the tail rod glass sealing ring.

5. The fully sealed device for small-size preform according to claim 2, characterized in that: The inner diameter and outer diameter of each section of the quartz sealing tube are the same.

6. The fully sealed device for small-size preform according to claim 2, characterized in that: The quartz sealing tube fixing base is provided with a groove which matches with the protrusion at the lower end of the quartz sealing tube.

7. The fully sealed device for small-size preform according to claim 2, characterized in that: The heights of the various sections of the quartz sealing tube are the same, and the height of each section of the quartz sealing tube is 200-400 mm. The inner diameter of each section of the quartz sealing tube is 15-40 mm larger than the diameter of the uniform preform rod.

8. The fully sealed device for small-size preform according to claim 4, characterized in that: The inner diameter of the tail rod glass sealing ring is 4-10mm larger than the outer diameter of the tail rod, the height of the tail rod glass sealing ring is 20-40mm, and the outer diameter of the tail rod glass sealing ring is 4-8mm smaller than the inner diameter of the groove at the upper end of the quartz sealing tube.

9. The fully sealed device for small-size preform according to claim 2, characterized in that: The flexible sealing member is a sealing soft felt matched with the tail rod, the inner diameter of the sealing soft felt is 2-5 mm smaller than the outer diameter of the tail rod, the inner wall of the quartz soft felt is provided with a cutout, the cutout length is 1-3 mm, the number of cutouts is 16-32, and the outer diameter of the sealing soft felt is 4-8 mm smaller than the outer diameter of the tail rod or the tail tube glass sealing ring groove.

10. The fully sealed device for small-size preform according to claim 2, characterized in that: The inner diameter of the sealing quartz pressure ring is 4-10mm larger than the outer diameter of the tail rod, the height of the sealing quartz pressure ring is 40-60mm, and the outer diameter of the sealing quartz pressure ring is 4-8mm smaller than the inner diameter of the groove at the upper end of the quartz sealing tube.

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