Seal device

Abstract

To provide a seal device in which a blade can move in a radial direction of an opening more securely than when an edge between a principal surface and an end surface of the blade is squarish.SOLUTION: There is provided a seal device 1 that has an opening 1H into which an optical fiber preform 200 can be inserted and closes a gap between the optical fiber preform 200 inserted into an upper opening 100H of an optical fiber drawing furnace 100 through the opening 1H and the upper opening 100H, and comprises a plurality of blades 10, 20 which can move in radial directions of the opening 1H and abut on a side face of the optical fiber preform 200, in which at least one blade between the plurality of blades 10, 20 has curved surfaces 11LC, 21TC which gradually vary in direction of inclination toward a vertical direction so that the blades 10, 20 decrease in thickness from at least one of a top surface as the uppermost surface in a height direction of the blade and a reverse surface as the lowermost surface in the height direction toward tip parts 10I, 20I closest to the center of the opening 1H.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a sealing device. [Background technology]

[0002] An optical fiber is manufactured by drawing an optical fiber preform. An optical fiber drawing furnace for drawing an optical fiber preform includes a furnace in which the optical fiber preform is housed, and the furnace is filled with an inert gas or other furnace gas. For this reason, a sealing device is sometimes used to close the upper end opening of the drawing furnace for housing the optical fiber preform in the furnace.

[0003] Such a sealing device is described in the following Patent Document 1. This sealing device has an opening through which an optical fiber preform can be inserted, and is equipped with a plurality of blades that are movable in the radial direction of the opening and have ends that can abut against the side surfaces of the optical fiber preform. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-152083 A Summary of the Invention [Problem to be solved by the invention]

[0005] In such a sealing device, there are cases where it is desired to move the optical fiber preform upward or downward with the side surface of the optical fiber preform in contact with the end of the blade. However, if the edge between the main surface and the end surface of the blade is sharp, the optical fiber preform may get caught by the blade, and the blade may not move in the radial direction of the opening.

[0006] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a seal device that allows the blade to move in the radial direction of the opening more reliably than when the edge between the main surface and end surface of the blade is sharp. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, aspect 1 of the present invention is a sealing device having an opening through which an optical fiber preform can be inserted, for sealing a gap between the upper opening and an optical fiber preform inserted from an upper opening of an optical fiber drawing furnace through the opening, the sealing device comprising a plurality of blades that are movable in a radial direction of the opening and can abut against a side of the optical fiber preform, and at least one of the plurality of blades has a curved surface in which the thickness gradient of the blade gradually decreases from at least one of an upper surface, which is the uppermost surface in the height direction of the blade, and a lower surface, which is the lowermost surface in the height direction, to a tip portion that protrudes most toward the center of the opening.

[0008] In the sealing device of this aspect, the blade having a curved surface does not have an angular edge between at least one of the upper surface and the lower surface and the tip. Therefore, when the optical fiber preform moves upward or downward, for example, even if the diameter of the optical fiber preform varies in the longitudinal direction of the optical fiber preform or the optical fiber preform is inclined, the optical fiber preform can contact the curved surface. Specifically, when a curved surface is provided from the upper surface to the tip of the blade, the optical fiber preform can contact the curved surface when the optical fiber preform moves downward, and when a curved surface is provided from the lower surface to the tip of the blade, the optical fiber preform can contact the curved surface when the optical fiber preform moves upward. Therefore, compared to when the edge between the main surface and the end surface of the blade is angular, in other words, when the edges between the upper surface and the lower surface of the blade and the tip of the blade are all angular, the optical fiber preform can be caught by the blade to suppress the blade from moving in the radial direction of the opening. Therefore, even when it is desired to move the optical fiber preform upward or downward with the side surface of the optical fiber preform abutting against the end of the blade, the blade can be moved more reliably in the radial direction of the opening, where upward means the direction in which the optical fiber preform moves away from the optical fiber drawing furnace and downward means the direction in which the optical fiber preform moves toward the optical fiber drawing furnace.

[0009] A second aspect of the present invention is the sealing device according to the first aspect, wherein the blade having the curved surface has the curved surface from the upper surface to the tip.

[0010] In this case, when the optical fiber preform moves downward, the curved surface can come into contact with the optical fiber preform, and the blade can move more reliably in the radial direction of the opening.

[0011] A third aspect of the present invention is the sealing device according to the first aspect, wherein the blade having the curved surface has the curved surface from each of the upper surface and the lower surface to the tip portion.

[0012] In this case, when the optical fiber preform moves downward and when it moves upward, the curved surface can come into contact with the optical fiber preform, and the blade can be moved in the radial direction of the opening more reliably.

[0013] A fourth aspect of the present invention is the sealing device according to any one of the first to third aspects, wherein the tip portion extends a predetermined distance along the height direction.

[0014] In this case, the contact area with the optical fiber preform can be increased at a portion of the optical fiber preform with a constant diameter or at a portion of the optical fiber preform with a general inclination angle that is inclined with respect to the longitudinal direction of the optical fiber preform, thereby improving the sealing performance of the optical fiber drawing furnace.

[0015] A fifth aspect of the present invention is the sealing device of any one of the first to fourth aspects, wherein the curved surface is a part of a torus surface.

[0016] Since the change in angle of the outer surface due to a change in the diameter of the optical fiber base material changes continuously in the longitudinal direction, when the curved surface is part of a torus surface, temporary deterioration in sealing performance due to sudden advancement or retreat of the blade can be avoided compared to when the curved surface is not part of a torus surface.

[0017] A sixth aspect of the present invention is a sealing device of any of the first to fifth aspects, characterized in that the plurality of blades include a first blade and a second blade arranged circumferentially offset from one another around the opening, the first blade including a first base extending along the circumferential direction, the second blade including a second base extending along the circumferential direction, the second base of the second blade overlapping from above with the first base of the first blade, and the first bases of the first blade overlapping from below with the second bases of adjacent second blades.

[0018] With such a sealing device, when the gas passes above the sealing device, the gas needs to change direction before flowing, and therefore the first and second blades that overlap in the height direction can improve the sealing performance of the optical fiber drawing furnace compared to a sealing device that is composed only of blades that do not overlap in the height direction.

[0019] Aspect 7 of the present invention is a sealing device of aspect 6, characterized in that the first blade and the second blade have the curved surface, and the curved surface of the first blade and the curved surface of the second blade are provided from the surface of the upper surface or the lower surface that is on the same side in the height direction to the tip portion.

[0020] With this sealing device, the first blade and the second blade can reliably move radially in the opening when they come into contact with an outer diameter fluctuating portion of the base material moving along a specific direction, compared to when the curved surfaces of the first blade and the second blade are not provided from the upper or lower surface on the same side in the height direction to the tip.

[0021] Aspect 8 of the present invention is a sealing device of aspect 6 or 7, characterized in that the multiple blades include a first blade and a second blade arranged adjacent to each other along a circumferential direction of the opening, the first blade includes a first base extending along the circumferential direction and an upper protrusion having a width smaller than that of the first base in the circumferential direction and protruding upward from any part other than the end of the first base, the second blade includes a second base extending along the circumferential direction and a lower protrusion having a width smaller than that of the second base in the circumferential direction and protruding downward from the second base, the second base overlaps the first base from above, the first base and the lower protrusion are arranged adjacent to each other along the circumferential direction, and the second base and the upper protrusion are arranged adjacent to each other along the circumferential direction.

[0022] In this case, the second base overlaps the first base from above, the first base and the lower protrusion are arranged adjacent to each other along the circumferential direction, and the second base and the upper protrusion are arranged adjacent to each other along the circumferential direction, so that the gas present below the sealing device needs to change direction and flow in order to pass through to above the sealing device. This can improve the sealing performance of the optical fiber drawing furnace compared to a case in which the first blade and the second blade, which do not have upper and lower protrusions and have flat surfaces over the entire width direction, are in contact with each other above and below in the height direction. Effect of the Invention

[0023] As described above, according to the present invention, a seal device is provided which allows the blade to move more reliably in the radial direction of the opening than when the edge between the main surface and the end surface of the blade is sharp. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic diagram of an optical fiber drawing furnace according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the sealing device of FIG. [Diagram 3] FIG. 3 is a perspective view showing a portion of the sealing device of FIG. 2. [Figure 4]FIG. 2 is a view of the first blade and the second blade viewed in the radial direction from the center side of the upper opening. [Diagram 5] 4 is a cross-sectional view of the first blade and the second blade at a position where the first blade and the second blade overlap each other. FIG. [Figure 6] 4 is a cross-sectional view of a first blade at a position where the first blade and the second blade do not overlap. FIG. [Figure 7] FIG. 4 is a cross-sectional view of the second blade at a position where the first blade and the second blade do not overlap. [Figure 8] 1 is a diagram showing an optical fiber preform being inserted into an optical fiber drawing furnace; [Figure 9] FIG. 4 is a cross-sectional view showing a first modified example of the first blade and the second blade. [Figure 10] FIG. 11 is a cross-sectional view showing a second modified example of the first blade and the second blade. [Figure 11] FIG. 11 is a cross-sectional view showing a fourth modified example of the first blade and the second blade. [Figure 12] FIG. 4 is a perspective view showing a part of a sealing device according to a different example from the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The sealing device according to the present invention will be illustrated below with reference to the accompanying drawings. The embodiments illustrated below are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention can be modified and improved without departing from the spirit of the present invention. In the drawings referred to below, the dimensions of each component may be changed to facilitate understanding.

[0026] Fig. 1 is a schematic diagram of an optical fiber drawing furnace according to an embodiment of the present invention. As shown in Fig. 1, the optical fiber drawing furnace 100 of this embodiment is a furnace that draws an optical fiber preform 200 to form an optical fiber 210, and mainly comprises a furnace tube 101, a heater 102, a heat insulating material 103, a housing 104, and a sealing device 1. The sealing device 1 of this embodiment is a sealing device for an optical fiber drawing furnace.

[0027] Although not shown, the optical fiber preform 200 is configured by surrounding the outer peripheral surface of a rod-shaped core glass body that becomes at least one core with a cladding glass body. The optical fiber preform 200 may include components other than the core glass body and the cladding glass body. A glass rod 220 for suspending the optical fiber preform 200 is connected to the upper part of the optical fiber preform 200.

[0028] The core tube 101 is a cylindrical member extending in the height direction of the optical fiber drawing furnace 100, and is capable of accommodating the optical fiber preform 200 in an internal space 101S. The inner and outer diameters of the core tube 101 are approximately constant in the extension direction of the core tube 101. The core tube 101 is made of, for example, quartz, carbon, or the like.

[0029] The heater 102 is a cylindrical heating element formed to surround the outer circumferential surface of the furnace core tube 101. An example of the heater 102 is a heater made of carbon. The heat insulating material 103 is configured to surround the heater 102 and the outer circumferential surface of the furnace core tube 101. The heat insulating material 103 is made of, for example, porous ceramic.

[0030] The housing 104 has a cylindrical peripheral wall that extends in the height direction of the optical fiber drawing furnace 100 and surrounds the outer circumferential surface of the thermal insulation material 103, and upper and lower walls that are connected to the upper and lower ends of the peripheral wall, sandwich the thermal insulation material 103 from above and below, and close the gap between the peripheral wall and the furnace core tube. The housing 104 may have a cooling function such as water cooling.

[0031] A lower housing 105 is provided below the furnace core tube 101. The upper part of the lower housing 105 is open so as to be connected to the internal space 101S of the furnace core tube 101, and the lower part is open so that the drawn optical fiber 210 can be led out.

[0032] An inert gas such as He, Ne, Ar, or N2 is filled into the internal space 101S of the furnace core tube 101. Note that a mixed gas in which another gas is added to the inert gas may be filled into the internal space 101S.

[0033] The upper part of the furnace tube 101 is open, and a sealing device 1 is disposed on the upper part of the furnace tube 101 and the housing 104. The sealing device 1 is a device for sealing the upper opening 100H of the optical fiber drawing furnace 100 together with the optical fiber preform 200 inserted from the upper opening 100H. Note that the upper part of the optical fiber preform 200 may be surrounded by a cover body 110 as shown in FIG.

[0034] Fig. 2 is a plan view of the sealing device 1, and Fig. 3 is a perspective view showing a part of the sealing device 1 of Fig. 2. As shown in Fig. 2 and Fig. 3, the sealing device 1 of the present embodiment includes a plurality of blades including a plurality of first blades 10 and a plurality of second blades 20, and a blade housing portion 30. The sealing device 1 is surrounded by the plurality of first blades 10 and the plurality of second blades 20, and has an opening 1H through which the optical fiber preform 200 can be inserted.

[0035] Each of the first blades 10 and each of the second blades 20 has a shape extending in the radial direction of the upper opening 100H. The first blades 10 are arranged radially at intervals along the circumferential direction of the upper opening 100H, and the second blades 20 are arranged radially at intervals along the circumferential direction of the upper opening 100H. The blade accommodating section 30 has a ring shape and has a first accommodating groove 31 in which the first blade 10 is accommodated and a second accommodating groove 32 in which the second blade 20 is accommodated. Note that, in FIG. 2, the blade accommodating section 30 is shown with the top cover removed, and the first accommodating groove 31 and the second accommodating groove 32 are visible, but in FIG. 3, the top cover is shown in an unremoved state, and therefore the first accommodating groove 31 and the second accommodating groove 32 are not visible. Each of the first blade 10 and the second blade 20 protrudes from the inner periphery of the blade housing section 30, is movable in the radial direction of the blade movement mechanism opening such as a spring with a shaft or an air cylinder (not shown), and is biased toward the center of the upper opening 100H by a biasing means such as a spring (not shown). Therefore, the first blade 10 and the second blade 20 can abut against the side of the optical fiber preform 100H inserted into the opening 1H. As shown in Figs. 2 and 3, the tip portions 10I and 20I of the first blade 10 and the second blade 20 that protrude most toward the center of the opening 1H are curved along the circumferential direction with a predetermined radius of curvature.

[0036] FIG. 4 is a view of the first blade 10 and the second blade 20 viewed from the center side of the opening 1H along the radial direction. The first blade 10 and the second blade 20 are arranged to be shifted from each other in the circumferential direction. The first blade 10 includes a first base 11 extending along the circumferential direction of the opening 1H, and an upper protrusion 12 having a width smaller than that of the first base 11 in the circumferential direction of the opening 1H and protruding upward from the first base 11 at any point other than the end of the first base 11. In FIG. 4, the upper protrusion 12 is provided approximately at the center of the first base 11 in the circumferential direction of the opening 1H. Therefore, the first blade 10 has a shape of an inverted T. The lower surface of the first blade 10 is the lower surface 11L of the first base 11, and the upper surface of the first blade 10 is composed of the upper surface 11T of the first base 11 and the upper surface 12T of the upper protrusion 12. Upper surface 12T is the uppermost surface in the height direction of first blade 10, and lower surface 11L is the lowermost surface in the height direction of first blade 10. The first blade is made of, for example, carbon, glass, SiC-coated carbon, or the like.

[0037] The second blade 20 includes a second base 21 extending along the circumferential direction of the upper opening 100H, and a lower protrusion 22 having a width smaller than that of the second base 21 in the circumferential direction of the upper opening 100H and protruding downward from the second base 21 at any point other than the end of the second base 21. In FIG. 4, the lower protrusion 22 is provided at approximately the center of the second base 21 in the circumferential direction of the opening 1H. Therefore, the second blade 20 has an approximately T-shaped shape. The upper surface of the second blade 20 is the upper surface 21T of the second base 21, and the lower surface of the second blade 20 is composed of the lower surface 21L of the second base 21 and the lower surface 22L of the lower protrusion 22. The upper surface 21T is the uppermost surface of the second blade 20 in the height direction, and the lower surface 22L is the lowermost surface of the second blade 20 in the height direction. The second blade is made of, for example, the material exemplified as the material of the first blade.

[0038] The first blades 10 and the second blades 20 are arranged in a staggered manner, with the second base 21 of one second blade 20 overlapping from above with each of a pair of first blades 10 adjacent to each other along the circumferential direction of the opening 1H, and the first base 11 of one first blade 10 overlapping from below with each of a pair of second blades 20 adjacent to each other along the circumferential direction of the opening 1H. In addition, a lower protrusion 22 is interposed between the first bases 11 of the adjacent first blades 10, and an upper protrusion 12 is interposed between the second bases 21 of the adjacent second blades 20. An upper surface 11T of the first base 11 of the first blade 10 and a lower surface 21L of the second base 21 of the second blade 20 face each other and are in contact with each other. In addition, the side surface 12S of the upper protrusion 12 of the first blade 10 faces the side surface 21S of the second base 21 of the second blade 20, and the side surface 22S of the lower protrusion 22 of the second blade 20 faces the side surface 11S of the first base 11 of the first blade 10. The protruding height of the upper surface 12T of the upper protrusion 12 of the first blade 10 from the upper surface 11T of the first base 11 is the same as the thickness of the second base 21 of the second blade 20. Therefore, the upper surface 12T of the upper protrusion 12 of the first blade 10 and the upper surface 21T of the second base 21 of the second blade 20 are located at approximately the same height. In addition, the protruding height of the lower surface 22L of the lower protrusion 22 of the second blade 20 from the lower surface 21L of the second base 21 is the same as the thickness of the first base 11 of the first blade 10. Therefore, the lower surface 22L of the lower protrusion 22 of the second blade 20 and the lower surface 11L of the first base portion 11 of the first blade 10 are located at approximately the same height. Except for the state in which the first blade 10 and the second blade 20 are moved to the innermost side of the upper opening 100H, a gap exists between the opposing side surfaces 12S and 21S, and a gap exists between the opposing side surfaces 22S and 11S.

[0039] FIG. 5 is a cross-sectional view along the radial direction and the vertical direction of the upper opening 100H at a portion where the first base portion 11 of the first blade 10 and the second base portion 21 of the second blade 20 overlap. This vertical direction can be expressed as the height direction of the first blade 10 and the second blade 20. Hereinafter, this height direction may be referred to as the vertical direction. As shown in FIG. 5, in this embodiment, the tip portion 10I of the first blade 10 extends a predetermined distance along the vertical direction, and the tip portion 20I of the second blade 20 extends a predetermined distance along the vertical direction. As described above, the tip portions 10I and 20I are curved along the circumferential direction with a predetermined radius of curvature, so that the tip portions 10I and 20I can each make surface contact with an outer peripheral surface having a radius of curvature of a predetermined diameter. From the viewpoint of preventing the occurrence of a gap between the optical fiber preform 200 and the tip portions 10I, 20I when the first blade 10 and the second blade 20 contact the side portion 201 of the optical fiber preform 200 as shown in FIG. 1, it is preferable that this diameter is the same as the radius of curvature of the side portion 201 at a portion where the diameter of the optical fiber preform 200 does not change or at a portion that is inclined with respect to the longitudinal direction of the optical fiber preform 200 in an optical fiber preform 200 having a general inclination angle.

[0040] The first blade 10 has a shape in which the edge on the tip side of the lower surface 11L is chamfered. That is, the first blade 10 has a lower curved surface 11LC in which the direction of inclination gradually approaches the vertical direction from the lower surface 11L to the tip portion 10I so that the thickness of the first blade 10 becomes smaller. Also, the second blade 20 has a shape in which the edge on the tip side of the upper surface 21T is chamfered. That is, the second blade 20 has an upper curved surface 21TC in which the direction of inclination gradually approaches the vertical direction from the upper surface 21T to the tip portion 20I so that the thickness of the second blade 20 becomes smaller. In this embodiment, the lower curved surface 11LC is a part of a torus surface, and the upper curved surface 21TC is a part of a torus surface different from the torus surface of the lower curved surface 11LC.

[0041] FIG. 6 is a cross-sectional view along the radial direction and the vertical direction of the upper opening 100H of the first blade 10 at a position where the first blade 10 and the second blade 20 do not overlap. In FIG. 6, the boundary between the first base 11 and the upper protrusion 12 is indicated by a broken line. As shown in FIG. 6, at a position where the first blade 10 and the second blade 20 do not overlap, the first blade 10 has a shape in which the edge on the tip side of the upper surface 12T of the upper protrusion 12 is chamfered. In other words, the first blade 10 has an upper curved surface 12TC whose inclination direction gradually approaches the vertical direction from the upper surface 12T of the upper protrusion 12 to the tip portion 10I so that the thickness of the first blade 10 becomes smaller. As shown in FIG. 3, in this embodiment, the upper curved surface 12TC is a part of the same torus surface as the torus surface of the upper curved surface 21TC.

[0042] FIG. 7 is a cross-sectional view along the radial direction and the vertical direction of the upper opening 100H of the second blade 20 at a position where the first blade 10 and the second blade 20 do not overlap. In FIG. 7, the boundary between the second base 21 and the lower protrusion 22 is indicated by a broken line. As shown in FIG. 7, at a position where the first blade 10 and the second blade 20 do not overlap, the second blade 20 has a shape in which the edge on the tip side of the lower surface 22L of the lower protrusion 22 is chamfered. In other words, the second blade 20 has a lower curved surface 22LC whose inclination direction gradually approaches the vertical direction from the lower surface 22L of the lower protrusion 22 to the tip 20I so that the thickness of the second blade 20 becomes smaller. As shown in FIG. 3, in this embodiment, the lower curved surface 22LC is a part of the same torus surface as the torus surface of the lower curved surface 11LC.

[0043] Next, the operation of the sealing device 1 will be described.

[0044] 8 is a diagram showing the state of the first blade 10 and the second blade 20 when the optical fiber preform 200 is inserted into the optical fiber drawing furnace 100. As shown in FIG. 8, when the optical fiber preform 200 is moved downward and inserted into the optical fiber drawing furnace 100, the tapered surface 202 of the optical fiber preform 200 may come into contact with the upper curved surface 21TC of the second blade 20. The inclination angle of such a tapered surface 202 is generally greater than 0 degrees and equal to or less than 20 degrees with respect to the axial direction of the optical fiber preform 200. In this case, when the optical fiber preform 200 moves downward, the upper curved surface 21TC is pressed by the tapered surface 202 toward the outer periphery in the radial direction of the upper opening 100H. As a result, the second blade 20 moves toward the outer periphery. Although not shown, the upper curved surface 12TC of the upper protrusion 12 of the first blade 10 is a part of the same torus surface as the torus surface of the upper curved surface 21TC, so that when the upper curved surface 21TC is pressed against the tapered surface 202, the upper curved surface 12TC is also pressed against the outer periphery by the tapered surface 202. Therefore, the first blade 10 moves toward the outer periphery in the same manner as the second blade 20. Therefore, the edge of the upper surface 11T of the first base portion 11 of the first blade 10 is prevented from contacting the optical fiber preform 200. In this manner, the optical fiber preform 200 is inserted into the internal space 101S of the optical fiber drawing furnace 100 in a state in which the first blade 10 and the second blade 20 are in contact with the optical fiber preform 200. Since the first blade 10 and the second blade 20 are in contact with the optical fiber preform 200 in this manner, the sealing device 1 closes the upper opening 100H of the optical fiber drawing furnace 100 together with the optical fiber preform 200 inserted from the opening 1H.

[0045] As described above, in the sealing device 1 of the present embodiment, the first blade 10 has the lower curved surface 11LC and the upper curved surface 12TC, and the second blade 20 has the upper curved surface 21TC and the lower curved surface 22LC. Therefore, when the optical fiber preform 200 moves in the vertical direction, even if the diameter of the optical fiber preform 200 becomes large, the optical fiber preform 200 has some unevenness, or the optical fiber preform 200 is inclined, the optical fiber preform 200 can contact these curved surfaces. Therefore, compared with the case where all edges between the upper and lower surfaces of the blades and the tip portions are angular, the first blade 10 and the second blade 20 can be prevented from not moving by being caught by the optical fiber preform 200, and the first blade 10 and the second blade 20 can be more reliably moved outward in the radial direction of the opening 1H. Therefore, even when it is desired to move the optical fiber preform 200 upward or downward with the side of the optical fiber preform 200 abutting the end of the first blade 10 or the second blade 20, the first blade 10 or the second blade 20 can be moved more reliably in the radial direction of the opening 1H.

[0046] In this embodiment, the lower curved surfaces 11LC, 22LC and the upper curved surfaces 21TC, 12TC are parts of a torus surface. Since the angle of the outer peripheral surface due to the change in the diameter of the optical fiber preform 200 changes continuously in the longitudinal direction, when the lower curved surfaces 11LC, 22LC and the upper curved surfaces 21TC, 12TC are parts of a torus surface, temporary deterioration of sealing performance due to abrupt forward or backward movement of the blade can be avoided compared to when the lower curved surfaces 11LC, 22LC and the upper curved surfaces 21TC, 12TC are not parts of a torus surface.

[0047] In this embodiment, the tip portions 10I and 20I are described as extending in the vertical direction. However, this embodiment is not limited to this, and the tip portions 10I and 20I do not have to extend in the vertical direction. In this case, for example, the upper curved surface 21TC contacts the lower surface 21L, the lower curved surface 11LC contacts the upper surface 11T, the upper curved surface 12TC contacts the lower curved surface 12LC, and the upper curved surface 21TC contacts the lower curved surface 22LC. In this embodiment, the tip portions 10I and 20I have a linear shape that follows the circumferential direction of the opening 1H.

[0048] In the present embodiment, the seal device 1 includes a first blade 10 and a second blade 20 arranged adjacent to each other along the circumferential direction of the opening 1H, the first blade 10 includes a first base 11 extending along the circumferential direction and an upper protrusion 12 having a width smaller than that of the first base 11 in the circumferential direction and protruding upward from any part of the first base 11 other than the end thereof, and the second blade 20 includes a second base 21 extending along the circumferential direction and a lower protrusion 22 having a width smaller than that of the second base 21 in the circumferential direction and protruding downward from the second base 21. The second base 21 overlaps the first base 11 from above, the first base 11 and the lower protrusion 22 are arranged adjacent to each other along the circumferential direction, and the second base 21 and the upper protrusion 12 are arranged adjacent to each other along the circumferential direction. For this reason, in order for the gas present below the sealing device 1 to pass through to the upper side of the sealing device 1, the gas needs to change direction and flow. Therefore, compared to a case in which the first blade and the second blade, which are not provided with the upper protrusion 12 and the lower protrusion 22 and have flat surfaces in the entire width direction, are in contact with each other above and below in the height direction, the sealing performance of the optical fiber drawing furnace 100 can be improved. Also, compared to a form in which the chamfered first blade 10 and the second blade 20 overlap in the height direction as shown in Figs. 9 to 11 described later, in the region where the first blade 10 and the second blade 20 overlap, a curved surface is not formed from the upper surface 11T to the tip 10I of the first blade 10, and a curved surface is not formed from the lower surface 21L to the tip 20I of the second blade 20, so that the cross-sectional area of ​​the gas passage may be reduced. Therefore, in this embodiment, the sealing performance of the optical fiber drawing furnace 100 can be improved compared to a case where a curved surface is formed from the upper surface 11T to the tip portion 10I of the first blade 10 and / or from the lower surface 21L to the tip portion 20I of the second blade 20. Furthermore, in this embodiment, when it is desired to move the optical fiber preform 200 upward or downward with the side surface of the optical fiber preform 200 abutting against the end of the first blade 10 or the second blade 20, the first blade 10 or the second blade 20 can be moved more reliably in the radial direction of the opening 1H. Therefore, according to this embodiment, it is possible to achieve both an improvement in the sealing performance of the optical fiber drawing furnace 100 and a more reliable movement of the first blade 10 or the second blade 20 in the radial direction of the opening 1H.

[0049] Next, a modified example of this embodiment will be described. Note that components that are the same as or equivalent to those in the above embodiment will be given the same reference numerals and will not be described again unless otherwise specified.

[0050] FIG. 9 is a cross-sectional view showing a first modified example of the first blade 10 and the second blade 20. As shown in FIG. 9, in this modified example, the position of the curved surface of the first blade 10 is different from that of the above embodiment. Specifically, the edge of the lower surface 11L of the first base portion 11 of the first blade 10 is angular, and the edge of the upper surface 11T of the first base portion 11 is chamfered. Therefore, the first blade 10 has an upper curved surface 11TC whose inclination direction gradually approaches the vertical direction from the upper surface 11T of the first base portion 11 to the tip portion 10I so that the thickness of the first blade 10 becomes smaller. In this modified example, the edge of the lower surface 22L of the lower protrusion 22 of the second blade 20 may be angular like the edge of the lower surface 11L of the first base portion 11. According to the sealing device 1 of this modified example, when the optical fiber preform 200 moves downward, the first blade 10 and the second blade 20 can move outward more reliably than when all edges between the upper and lower surfaces of the blades and the tip portions are angular. In this modification, the tip portions 10I and 20I do not have to extend in the vertical direction. In this case, for example, the upper curved surface 21TC contacts the lower surface 21L, and the upper curved surface 11TC contacts the lower surface 11L. In this embodiment, the tip portions 10I and 20I have a linear shape that is aligned with the circumferential direction of the opening 1H.

[0051] FIG. 10 is a cross-sectional view showing a second modified example of the first blade 10 and the second blade 20. As shown in FIG. 10, the first blade 10 and the second blade 20 of this modified example are different from the first blade 10 and the second blade 20 of the above embodiment in that the edge of the upper surface 11T of the first base portion 11 of the first blade 10 is chamfered, and the edge of the lower surface 21L of the second base portion 21 of the second blade 20 is chamfered. Therefore, the first blade 10 has an upper curved surface 11TC whose inclination direction gradually approaches the vertical direction from the upper surface 11T of the first base portion 11 to the tip portion 10I so that the thickness of the first blade 10 becomes smaller. In addition, the second blade 20 has a lower curved surface 21LC whose inclination direction gradually approaches the vertical direction from the lower surface 21L of the second base portion 21 to the tip portion 20I so that the thickness of the second blade 20 becomes smaller. In this modification, the tip 10I does not extend in the vertical direction, and the upper curved surface 11TC and the lower curved surface 11LC of the first base 11 of the first blade 10 are connected, and the upper curved surface 11TC and the lower curved surface 11LC are part of the same torus surface. Also, the tip 20I does not extend in the vertical direction, and the upper curved surface 21TC and the lower curved surface 21LC of the second base 21 of the second blade 20 are connected, and the upper curved surface 21TC and the lower curved surface 21LC are part of the same torus surface. Therefore, the tip portions 10I and 20I have a linear shape along the circumferential direction of the opening 1H. The torus surfaces of the upper curved surface 11TC and the lower curved surface 11LC and the torus surfaces of the upper curved surface 21TC and the lower curved surface 21LC are different from each other. According to the sealing device 1 of this modification, when the optical fiber preform 200 moves downward, the first blade 10 and the second blade 20 can be moved outward more reliably than when the edges between the upper and lower surfaces of the blades and the tips are all angular. In this embodiment, the tips 10I, 20I may extend in the up-down direction.

[0052] FIG. 11 is a cross-sectional view showing a third modified example of the first blade 10 and the second blade 20. As shown in FIG. 11, in this modified example, the position of the curved surface of the second blade 20 is different from that of the above embodiment. Specifically, the edge of the upper surface 21T of the second base portion 21 of the second blade 20 is angular, and the edge of the lower surface 21L of the second base portion 21 is chamfered. Therefore, the second blade 20 has a lower curved surface 21LC whose inclination direction gradually approaches the vertical direction from the lower surface 21L of the second base portion 21 to the tip portion 20I so that the thickness of the second blade 20 becomes smaller. In this modified example, the edge of the upper surface 12T of the upper protrusion 12 of the first blade 10 may be angular like the edge of the upper surface 21T of the second base portion 21. According to the sealing device 1 of this modified example, when the optical fiber preform 200 moves upward, the first blade 10 and the second blade 20 can move outward more reliably than when all edges between the upper and lower surfaces of the blades and the tip portions are angular. In this modification, the tip portions 10I, 20I do not have to extend in the vertical direction. In this case, for example, the lower curved surface 21LC contacts the upper surface 21T, and the lower curved surface 11LC contacts the upper surface 11T. In this embodiment, the tip portions 10I, 20I have a linear shape that is aligned with the circumferential direction of the opening 1H.

[0053] 9 to 11, the curved surface of the first blade 10 and the curved surface of the second blade 20 are provided from the upper surface 11T, 21T and the lower surface 11L, 21L on the same side in the height direction to the tip portions 10I, 20I. With this configuration, when the curved surfaces of the first blade 10 and the second blade 20 abut against the outer diameter fluctuating portion of the optical fiber preform 200 moving along a specific direction, the first blade 10 and the second blade 20 can reliably move in the radial direction of the opening 1H, compared to a case where the curved surfaces are not provided from the upper surface 11T, 21T and the lower surface 11L, 21L on the same side in the height direction to the tip portions.

[0054] Although the present invention has been described above using the above-mentioned embodiment and modified examples as examples, the present invention is not limited to these.

[0055] For example, in the above embodiment, the first blade 10 has the upper protrusion 12, and the second blade 20 has the lower protrusion 22. However, the blades of the seal device 1 of the present invention are not limited to the above embodiment. FIG. 12 is a perspective view showing a part of the seal device 1 of an example different from the above embodiment. As shown in FIG. 12, the seal device 1 of this example is different from the seal device 1 of the above embodiment in that the first blade 10 does not have the upper protrusion 12, and the second blade 20 does not have the lower protrusion 22. That is, in this example, the first blade 10 is made of the first base 11, and the second blade 20 is made of the second base 21. In this embodiment, the first blade 10 has an upper curved surface 11TC and a lower curved surface 11LC, and the second blade 20 has an upper curved surface 21TC and a lower curved surface 21LC, similarly to the above embodiment and each modified example. In this example, as in the above embodiment, when the optical fiber preform 200 moves upward or downward, the first blade 10 and the second blade 20 can move outward more reliably than when the edges between the upper and lower surfaces of the blades and their tips are all angular.

[0056] In the above embodiment and modified examples, the upper curved surfaces 11TC, 12TC, 21TC and the lower curved surfaces 11LC, 21LC, 22LC are described as being parts of a torus surface. However, the upper curved surfaces 11TC, 12TC of the first blade 10 may have an inclination direction gradually approaching the vertical direction from the upper surface 11T, 12T to the tip 10I so that the thickness of the first blade 10 decreases, and the upper curved surface 21TC of the second blade 20 may have an inclination direction gradually approaching the vertical direction from the upper surface 21T to the tip 20I so that the thickness of the second blade 20 decreases, and they do not have to be parts of a torus surface. Similarly, the lower curved surface 12LC of the first blade 10 may have a slope that gradually approaches the vertical direction from the lower surface 11L to the tip 10I so that the thickness of the first blade 10 decreases, and the lower curved surfaces 21LC, 22LC of the second blade 20 may have a slope that gradually approaches the vertical direction from the lower surfaces 21L, 22L to the tip 20I so that the thickness of the second blade 20 decreases, and they do not have to be part of a torus surface.

[0057] In the above embodiment and modified example, all of the first blades 10 and the second blades 20 have at least one of the upper curved surfaces 11TC, 12TC, 21TC and the lower curved surfaces 11LC, 21LC, 22LC. However, some of the first blades 10 and the second blades 20 may not have these upper curved surfaces or lower curved surfaces, and the edges between the upper and lower surfaces and the tips of these first blades 10 and the second blades 20 may all be angular. Even in this case, the first blades 10 and the second blades 20 can be moved outward more reliably than when all of the first blades 10 and the second blades 20 do not have the upper curved surfaces or lower curved surfaces, and the edges between the upper and lower surfaces and the tips of these tips are all angular.

[0058] In the above embodiment, nothing is provided on the upper part of the sealing device 1. However, for example, a shield pipe surrounding the outer circumferential surface of the optical fiber preform 200 may be provided on the upper part of the sealing device 1.

[0059] In the above embodiment and modified example, the first blade 10 and the second blade 20 are described as being multiple in number, but the present invention may have only one first blade 10 and one second blade 20. In this case, the other blades do not need to be vertically overlapped. [Industrial Applicability]

[0060] As described above, according to the present invention, a sealing device is provided that allows the blade to move more reliably than when the edge between the main surface and end surface of the blade is sharp, and is expected to be used in the field of optical fiber manufacturing. [Explanation of symbols]

[0061] 1. Sealing device 10. First blade 10I...Tip 11...1st base 11TC...Upper curved surface 11LC...Lower curved surface 12...Upper protrusion 12TC ··· Upper surface 20 ··· Second blade 20I ··· Tip 21 ··· Second base 21TC ··· Upper surface 21LC ··· Lower surface 22 ··· Lower protruding part 22LC ··· Lower surface 100 ··· Optical fiber wire drawing furnace 200 ··· Optical fiber base material

Claims

1. 1. A sealing device having an opening through which an optical fiber preform can be inserted, the sealing device being configured to close a gap between an optical fiber preform inserted from an upper opening of an optical fiber drawing furnace through the opening and the upper opening, a plurality of blades movable in a radial direction of the opening and capable of contacting a side surface of the optical fiber preform; At least one of the plurality of blades has a curved surface whose inclination direction gradually approaches the height direction from at least one of an upper surface, which is the uppermost surface in the height direction of the blade, and a lower surface, which is the lowermost surface in the height direction, to a tip portion that protrudes most toward the center of the opening so that the thickness of the blade becomes smaller. A sealing device characterized by:

2. The blade having the curved surface has the curved surface from the upper surface to the tip portion. The sealing device according to claim 1 .

3. The blade having the curved surface has the curved surface from each of the upper surface and the lower surface to the tip portion. The sealing device according to claim 1 .

4. The tip portion extends a predetermined distance along the height direction. The sealing device according to claim 1 .

5. The curved surface is a part of a torus surface. The sealing device according to claim 1 .

6. The plurality of blades include a first blade and a second blade that are arranged to be shifted in a circumferential direction of the opening, The first blade includes a first base portion extending along the circumferential direction, The second blade includes a second base portion extending along the circumferential direction, the second base portion of the second blade overlaps the first base portion of the first blade from above, The first base portion of the first blade overlaps the second base portion of the second blade adjacent to each other from below. The sealing device according to any one of claims 1 to 5.

7. the first blade and the second blade have the curved surface, The curved surface of the first blade and the curved surface of the second blade are provided from one of the upper surface and the lower surface on the same side in the height direction to the tip portion. The sealing device according to claim 6 .

8. the first blade includes an upper protruding portion having a width smaller than a width of the first base portion in the circumferential direction and protruding upward from any portion other than an end portion of the first base portion, the second blade includes a lower protruding portion that has a width smaller than a width of the second base portion in the circumferential direction and protrudes downward from the second base portion, The first base portion and the lower protrusion portion are arranged adjacent to each other along the circumferential direction, and the second base portion and the upper protrusion portion are arranged adjacent to each other along the circumferential direction. The sealing device according to claim 6 .

Images