Abstract: A glass base material elongating method of sequentially feeding rod-like glass base materials hung by a glass base material feeding mechanism into a heating furnace, and pulling a glass rod with a smaller diameter by a pulling chuck at a lower part of the heating furnace, includes: aligning, by an alignment guiding device that guides the glass rod, a guiding center of the alignment guiding device with an axis of the glass rod, the alignment guiding device guiding the glass rod between the heating furnace and the pulling chuck.

Abstract: To restrict deterioration of non-circularity in a constricted portion of an optical fiber preform, provided is an optical fiber preform manufacturing method including introducing inert gas along a surface of the optical fiber preform, causing the inert gas to circulate around the optical fiber preform with an axis of the optical fiber preform in a longitudinal direction as a center, and heating the optical fiber preform in an inert gas environment. In this manufacturing method, the inert gas may be introduced in a direction parallel to a tangent line of the optical fiber preform in a plane orthogonal to the axis.

Abstract: A sintering apparatus for sintering a porous glass base material, including a furnace core tube surrounded by heaters, the furnace core tube housing the porous glass base material; a lid member having an insertion hole through which a holding rod coupled with the porous glass base material is inserted, the lid member mounted at one end of the furnace core tube; a sealing chamber having a supply port that introduces seal gas and a discharging port that discharges the seal gas, the sealing chamber provided at the lid member covering the insertion hole; and a cylindrical member that causes a pressure difference between gas inside of the tube of an inside the furnace core tube and gas inside of the sealing chamber to be generated while the holding rod is inserted through the cylindrical member inside of the sealing chamber.

Abstract: A method of elongating a glass base material to obtain a glass rod having a smaller diameter, using a glass base material elongating apparatus including a feeder at least for the glass base material, a heating furnace, and an elongating mechanism of the glass base material below the heating furnace, is such that a horizontal plane position measuring unit of the glass base material is provided inside or near the heating furnace, the feeder has a glass base material horizontal plane position adjusting unit, and the elongating mechanism has three or more sets of elongating rollers capable of switching between grasping and releasing for keeping the position of the glass rod in the horizontal plane to be constant, and the glass base material is elongated with the position thereof in the horizontal plane kept as targeted by controlling the glass base material horizontal plane position adjusting unit.

Abstract: A flange fixing structure is provided that fixes flange parts respectively provided to two pipe conduits by means of a fixture in a butting manner via a gasket. In this flange fixing structure, when an effective length of the fixture is denoted by L0, a linear expansion coefficient of the fixture is denoted by ?0, thicknesses of n (where n is an integer of 1 or more) members held by the fixture are respectively denoted by t1 to tn, and linear expansion coefficients of the n members are respectively denoted by ?1 to ?n, a product L0?0 of the effective length L0 of the fixture and the linear expansion coefficient ?0 of the fixture is substantially equal to a sum ?ti?i (i=1 to n) of products of the respective thicknesses t1 to tn and the respective linear expansion coefficients ?1 to ?n.

Abstract: Provided is a glass base material hanging mechanism that, when hanging a starting member or a glass base material, can tightly (solidly) connect the hanging shaft tube and the hanging component and can vertically align the hanging component and the center of the glass base material.

Abstract: A gripping mechanism includes: a plurality of chuck claws that, when having come close to each other, generate a gripping force on a gripped body; a chuck body that holds the plurality of chuck claws on a common planar surface, and moves them on the planar surface; and a plurality of chuck plates that, when each of the plurality of chuck claws grips the gripped body, are interposed between each of the plurality of chuck claws and the gripped body, wherein a thermal expansion coefficient ?l of the plurality of chuck claws, a thermal expansion coefficient ?2 of the plurality of chuck plates and a thermal expansion coefficient ?W of the gripped body has a relationship indicated by Equation 1: ?W<?1<?2 ??(Equation 1)

Abstract: A porous glass base material sintering method comprising measuring a feeding speed Vf of a porous glass base material and a movement speed Vw of a bottom end of the glass base material; performing a sintering treatment of the porous glass base material presetting, for each feeding distance L of the porous glass base material, a greater-than-1 target value ?S (L) of an elongation rate in a straight body portion of the porous glass base material calculated based on a ratio Vw/Vf, and controlling at least one of a temperature of the heating furnace and a feeding speed of the porous glass base material such that a measured value ? of the elongation rate of the porous glass base material matches with the target value ?S (L).

Abstract: A sintering apparatus for sintering a porous glass base material, including a furnace core tube surrounded by heaters, the furnace core tube housing the porous glass base material; a lid member having an insertion hole through which a holding rod coupled with the porous glass base material is inserted, the lid member mounted at one end of the furnace core tube; a sealing chamber having a supply port that introduces seal gas and a discharging port that discharges the seal gas, the sealing chamber provided at the lid member covering the insertion hole; and a cylindrical member that causes a pressure difference between gas inside of the tube of an inside the furnace core tube and gas inside of the sealing chamber to be generated while the holding rod is inserted through the cylindrical member inside of the sealing chamber.

Abstract: Provided is a glass base material elongating method of using a glass base material elongation apparatus including a heating furnace, a feeding mechanism, and a pulling mechanism to elongate the rod-shaped glass base material to form a thinner glass rod, the method comprising gripping a pulling dummy rod connected to a bottom end of the glass base material with first pulling rollers of the pulling mechanism and, together with the feeding mechanism, feeding the glass base material to the heating furnace; and before a pulling force necessary for pulling the pulling dummy rod to elongate the glass base material reaches a load force that causes slipping between the pulling dummy rod and the first pulling rollers, gripping and pulling the pulling dummy rod with second pulling rollers of the pulling mechanism in addition to the first pulling rollers.

Abstract: A glass base material elongating method of sequentially feeding rod-like glass base materials hung by a glass base material feeding mechanism into a heating furnace, and pulling a glass rod with a smaller diameter by a pulling chuck at a lower part of the heating furnace, includes: aligning, by an alignment guiding device that guides the glass rod, a guiding center of the alignment guiding device with an axis of the glass rod, the alignment guiding device guiding the glass rod between the heating furnace and the pulling chuck.

Abstract: The present invention provides an apparatus for sintering a glass preform for an optical fiber, wherein the glass preform for the optical fiber is received in a muffle tube and is heated in an atmospheric gas while being suspended on a shaft and supported thereon, the apparatus comprising: a first gas seal that is provided at an upper end of the muffle tube, the shaft being inserted therethrough; a buffering chamber that is provided above the first gas seal and that covers the shaft; a second gas seal that is provided at an upper end of the buffering chamber, the shaft being inserted therethrough; and a unit that introduces the atmospheric gas exhausted from the muffle tube into the buffering chamber.

Abstract: In a method of forming a conical shape on a glass rod including an effective portion and an ineffective portion adjoining the effective portion to form a conical shape in the effective portion by simultaneously heating a boundary and the vicinity of the boundary between the effective portion and the ineffective portion and pulling an end of the ineffective portion, the temperature of a heater is raised and a heating target on the glass rod is simultaneously moved from the ineffective portion to the boundary.

Abstract: A glass base material elongating method of sequentially feeding rod-like glass base materials hung by a glass base material feeding mechanism into a heating furnace, and pulling a glass rod with a smaller diameter by a pulling chuck at a lower part of the heating furnace, includes: aligning, by an alignment guiding device that guides the glass rod, a guiding center of the alignment guiding device with an axis of the glass rod, the alignment guiding device guiding the glass rod between the heating furnace and the pulling chuck.

Abstract: A flange fixing structure is provided that fixes flange parts respectively provided to two pipe conduits by means of a fixture in a butting manner via a gasket. In this flange fixing structure, when an effective length of the fixture is denoted by L0, a linear expansion coefficient of the fixture is denoted by ?0, thicknesses of n (where n is an integer of 1 or more) members held by the fixture are respectively denoted by t1 to tn, and linear expansion coefficients of the n members are respectively denoted by ?1 to ?n, a product L0?0 of the effective length L0 of the fixture and the linear expansion coefficient ?0 of the fixture is substantially equal to a sum ?ti?i (i=1 to n) of products of the respective thicknesses t1 to tn and the respective linear expansion coefficients ?1 to ?n.

Abstract: Provided is a glass base material elongation method for elongating a glass base material with a large diameter to manufacture a glass rod with a smaller diameter, the method comprising, when elongating a glass base material that has a transparent glass tapered portion at one end of a trunk portion and a glass tapered portion including a non-transparent glass portion at the other end of the trunk portion, prior to the elongation, fusing a hanging dummy to an end of the transparent glass tapered portion, setting the hanging dummy in communication with a feeding mechanism, inserting the glass base material into a heating furnace beginning with the other end, and performing elongation.

Abstract: To prevent constriction machining from reducing usage efficiency of a glass rod, provided is a glass rod machining method including softening of softening a portion of the glass rod by heating the portion of the glass rod, and constricting of forming a constricted shape in the glass rod by moving one end of the glass rod relative to the other end of the glass rod at a constriction speed satisfying a condition that a constriction load acting as a tensile force on the glass rod does not extend beyond a predetermined range. In this method, the constricting includes, when constriction speed increases, making an adjustment to decrease a heating temperature of the glass rod. This method may include determining of determining the heating temperature of the glass rod during the constricting by referencing a heating temperature table in which heating temperatures corresponding to the constriction speed are stored in advance.

Abstract: In order to provide a glass base material elongating apparatus that can safely elongate a glass base material in an extendable top chamber without damaging a flange, provided is a glass base material elongating apparatus comprising a heating furnace; an extendable top chamber formed of a multilayer cylinder disposed above the heating furnace; a glass base material hanging mechanism that hangs a glass base material into the heating furnace and the extendable top chamber; and a top chamber lifting mechanism. A flange is formed on a top portion of an outermost tube of the multilayer cylinder, and the top chamber lifting mechanism includes a cylinder support member that supports the flange from below and a cylinder lifting member that lifts up the cylinder support member.

Abstract: The present invention provides an apparatus and a method for fabricating a glass rod from a glass preform capable of suppressing a diameter fluctuation of the drawn glass rod even when there is a relatively large diameter reduction ratio between the glass preform and the glass rod, such as 60 to 95%. The feed speed V1 of the glass preform is set to a constant value, the diameter D of the glass preform is acquired for determining the drawing speed V2 from diameter data of the glass preform measured before being drawn at a diameter acquisition position defined with respect to a reference position of the furnace. The distance from the reference position to the diameter acquisition position is defined so as to vary depending on a diameter fluctuation of the glass preform before being drawn in a longitudinal direction thereof.

Abstract: The present invention provides an apparatus for sintering a glass preform for an optical fiber, wherein the glass preform for the optical fiber is received in a muffle tube and is heated in an atmospheric gas while being suspended on a shaft and supported thereon, the apparatus comprising: a first gas seal that is provided at an upper end of the muffle tube, the shaft being inserted therethrough; a buffering chamber that is provided above the first gas seal and that covers the shaft; a second gas seal that is provided at an upper end of the buffering chamber, the shaft being inserted therethrough; and a unit that introduces the atmospheric gas exhausted from the muffle tube into the buffering chamber.