Graphite furnace and optimization method for reducing power of graphite furnace

Abstract

The invention relates to a graphite furnace and an optimization method for reducing the power of the graphite furnace, and the graphite furnace is used for optical fiber drawing. The graphite central pipe penetrates through the hearth along the longitudinal axis of the furnace body; the induction coil is arranged around the periphery of the graphite central tube; the convex bottom plate is hermetically fixed at the lower end opening of the furnace body; the shaping muffle tube is embedded into the convex bottom plate and is coaxially positioned with the convex bottom plate, and the inlet end of the shaping muffle tube abuts against the outlet end of the graphite center tube; an arc-shaped reflecting surface is arranged on one side, facing the hearth, of the inner wall of the shaping muffle tube; and the annealing pipe is connected with an outlet of the shaping muffle pipe. According to the invention, heat dissipated downwards is reflected back to the hearth through the arc-shaped reflecting surface by the convex bottom plate, and is superposed with the lower heat transfer area to form a composite thermal field, so that the central position of the heat area is kept constant while the electric energy demand is reduced, the diameter fluctuation of the optical fiber cladding is obviously reduced, and the upward movement of the heat area caused by the aging of the graphite central tube is counteracted; and the stable process period is prolonged.

Description

Technical Field

[0001] This invention relates to the field of optical fiber manufacturing equipment technology, and in particular to a graphite furnace and an optimized method for reducing the power of the graphite furnace. Background Technology

[0002] In optical fiber drawing, the graphite furnace, as the core heating equipment, directly determines production costs and process stability through its power consumption. Existing graphite furnaces generally employ a concave bottom plate structure, which has revealed the following drawbacks during long-term operation: Uneven heat distribution: The concave shape causes heat to accumulate in the upper part of the furnace, requiring a high power of ≥60 kW to compensate for heat loss at the bottom; Power increases with operating time: After 180 days of continuous use, the turning power increases by an average of 5–6 kW, and the aging of the bottom graphite parts accelerates. Poor process stability: thermal zone offset caused the fiber cladding diameter 3σ to fluctuate by up to 0.8 μm, with a pass rate of only 92.3%. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a graphite furnace and an optimized method for reducing the power of the graphite furnace. The convex bottom plate reflects the heat at the bottom of the furnace upward and superimposes it with the hot zone of the induction coil to form a composite hot field, making the energy of the hot zone more concentrated and the position more stable.

[0004] To solve the above-mentioned technical problems, the present invention provides a graphite furnace for optical fiber drawing, comprising: The furnace body has an internal furnace chamber. A graphite central tube extends through the furnace chamber along the longitudinal axis of the furnace body; An induction coil is arranged around the outer periphery of the graphite central tube to generate a high-frequency electromagnetic field to heat the graphite central tube. The convex bottom plate is sealed and fixed to the lower opening of the furnace body. A shaped muffle tube is embedded in the convex base plate and positioned coaxially therewith. Its inlet end abuts against the outlet end of the graphite central tube and is used to radially shape the fiber cladding. An arc-shaped reflective surface is provided on the inner wall of the shaped muffle tube facing the furnace. The annealing tube, connected to the outlet of the shaped muffle tube, is used to anneal the drawn optical fiber.

[0005] In one embodiment of the present invention, the convex bottom plate includes a protruding connector and a bottom plate; the protruding connector is annular, and its outer periphery is sealed to the lower opening of the furnace body, and the bottom plate is connected to the protruding connector.

[0006] In one embodiment of the present invention, a first through hole is formed at the center of the protruding connector; the base plate is embedded and fixed in the first through hole, and a second through hole coaxial with the first through hole is formed at the center of the base plate, and the two through holes together form a continuous heat flow channel.

[0007] In one embodiment of the present invention, the protruding connector is provided with a plurality of threaded blind holes, and the bolt passes through the threaded blind holes to fix the lower end opening of the furnace body.

[0008] In one embodiment of the present invention, the height of the protruding connector protruding from the lower end opening of the furnace body is 10mm ± 1mm.

[0009] In one embodiment of the present invention, the protruding connector is made of TC4 titanium alloy.

[0010] In one embodiment of the present invention, the induction coil is a 265 type coil with a wire diameter of 8mm and a turn spacing of 3mm.

[0011] In one embodiment of the present invention, the induction coil has 10 turns.

[0012] In one embodiment of the present invention, a protective sleeve is provided on the outside of the annealing tube.

[0013] Secondly, in order to solve the above-mentioned technical problems, the present invention provides an optimized method for reducing the power of a graphite furnace, comprising: S1: A convex bottom plate is provided at the lower opening of the furnace body, such that the convex connecting piece of the convex bottom plate protrudes out of the lower opening of the furnace body by 10 mm ± 1 mm. S2: Synchronously incrementally match the height of the graphite central tube so that the graphite central tube abuts against the protruding connector; S3: Increase the number of turns of the induction coil to 10 and move the entire induction coil down by 8-10 mm, so that the center of the hot zone moves down and forms a composite hot field with the arc-shaped reflective surface of the shaped muffle tube.

[0014] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: The graphite furnace and the optimized method for reducing graphite furnace power described in this invention use an outwardly convex bottom plate to reflect the heat lost downwards back into the furnace chamber, which superimposes with the heat zone generated by the induction coil to form a composite thermal field. This reduces the power demand while keeping the center position of the heat zone constant, significantly reducing the fluctuation of the fiber cladding diameter. As a result, the input power of the graphite furnace at the same drawing temperature is significantly reduced, and the power no longer increases with the running time. This enables long-cycle, low-energy-consumption, and stable production. Furthermore, it can also offset the upward shift of the heat zone caused by the aging of the graphite central tube, extending the stable process cycle. Attached Figure Description

[0015] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0016] Figure 1 This is a schematic diagram of the graphite furnace in a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the protruding connector in this invention; The following are the markings on the attached diagrams in the instruction manual: 1. Furnace body; 2. Graphite center tube; 3. Induction coil; 4. Molded muffle tube; 5. Annealing tube; 6. Base plate; 7. Protruding connector; 8. Sheath. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0018] Reference Figure 1-2 As shown, the present invention provides a graphite furnace for optical fiber drawing, comprising: Furnace body 1, with an internal furnace chamber; The graphite central tube 2 penetrates the furnace chamber along the longitudinal axis of the furnace body 1; An induction coil 3 is arranged around the outer periphery of the graphite central tube 2 to generate a high-frequency electromagnetic field to heat the graphite central tube 2. The convex bottom plate is sealed and fixed to the lower opening of the furnace body 1; The shaped muffle tube 4 is embedded in the convex base plate and positioned coaxially with it. Its inlet end abuts against the outlet end of the graphite central tube 2 and is used to radially shape the fiber cladding. Annealing tube 5, connected to the outlet of shaped muffle tube 4, is used to anneal the drawn optical fiber.

[0019] Preferably, the convex base plate includes a protruding connector 7 and a base plate 6; the protruding connector 6 is annular, and its outer periphery is sealed to the lower opening of the furnace body 1, and the base plate 6 is connected to the protruding connector 6. The protruding connector 7 is made of TC4 titanium alloy. Its high-temperature strength and oxidation resistance are superior to traditional graphite base plates, extending the base plate's lifespan and reducing thermal drift caused by base plate deformation.

[0020] Furthermore, a first through hole is formed at the center of the protruding connector 6; the base plate 7 is embedded and fixed in the first through hole, and a second through hole coaxial with the first through hole is formed at the center of the base plate 6, the two through holes together forming a continuous heat flow channel.

[0021] In this embodiment, the protruding connector 6 is provided with several threaded blind holes, and the bolt passes through the threaded blind holes to fix the lower opening of the furnace body 1.

[0022] The protruding connector 6 protrudes 10 mm ± 1 mm from the lower opening of the furnace body 1. This 10 mm ± 1 mm protrusion matches the height increment of the graphite central tube 2, ensuring continuous heat flow channels, reducing interfacial thermal resistance, and improving thermal repeatability.

[0023] Furthermore, an arc-shaped reflective surface is provided on the inner wall of the shaped muffle tube 4 facing the furnace. The arc surface of the inner wall of the shaped muffle tube 4 reflects the lost heat back to the optical fiber region, further equalizing the radial temperature and suppressing cladding diameter fluctuations.

[0024] Preferably, the induction coil 3 is a 265 type coil with a wire diameter of 8mm and a turn spacing of 3mm. Increasing the number of turns and reducing the turn spacing for the same length results in a more concentrated magnetic field, a lower and steeper heat distribution zone, and reduced heat waste in the upper part of the furnace.

[0025] Preferably, the induction coil 3 has 10 turns. Increasing the original 6-turn induction coil 3 to 10 turns increases the concentration of the magnetic field distribution.

[0026] In addition, a sheath 8 is provided on the outside of the annealing tube 5. The sheath 8 can block environmental convection, reduce sudden temperature gradient changes in the annealing section, reduce residual stress in the optical fiber, and improve the strength of subsequent cabling.

[0027] Based on the above-described graphite furnace structure, during operation, the optical fiber rod enters the graphite central tube 2 through the furnace body 1 inlet; the induction coil 3 generates a high-frequency electromagnetic field on the outer periphery of the graphite central tube, causing the tube wall to heat up rapidly, forming a downward-moving and concentrated high-temperature zone. Simultaneously, the protruding connector 6, with an outward protrusion height of 10 cm, reflects the heat that was originally dissipated downwards upwards, superimposing it with the hot zone of the induction coil 3 to form a focused-reflection composite thermal field. Energy is then refocused onto the outer surface of the optical fiber rod, achieving a reduction in input power at the same drawing temperature. The heated and softened optical fiber rod then passes sequentially through a coaxially abutting shaped muffle tube 4 and an annealing tube 5: the shaped muffle tube 4 provides radial constraint and preliminary shaping of the fiber cladding, while the annealing tube 5 provides a controllable temperature gradient to eliminate residual stress.

[0028] This invention provides a graphite furnace optimization method, comprising: S1: A convex bottom plate is provided at the lower opening of the furnace body 1, such that the convex connecting piece 7 of the convex bottom plate protrudes out of the lower opening of the furnace body 1 by 10 mm ± 1 mm. S2: Synchronously incrementally match the height of the graphite central tube 2 so that the graphite central tube 2 abuts against the protruding connector 7; S3: Increase the number of turns of the induction coil 3 to 10 and move the entire induction coil 3 down by 8-10 mm, so that the center of the hot zone moves down and forms a composite hot field with the arc-shaped reflective surface of the shaped muffle tube 4.

[0029] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A graphite furnace for drawing optical fibers, characterized in that, include: The furnace body has an internal furnace chamber. A graphite central tube extends through the furnace chamber along the longitudinal axis of the furnace body; An induction coil is arranged around the outer periphery of the graphite central tube to generate a high-frequency electromagnetic field to heat the graphite central tube. The convex bottom plate is sealed and fixed to the lower opening of the furnace body. A shaped muffle tube is embedded in the convex base plate and positioned coaxially therewith. Its inlet end abuts against the outlet end of the graphite central tube and is used to radially shape the fiber cladding. An arc-shaped reflective surface is provided on the inner wall of the shaped muffle tube facing the furnace. The annealing tube, connected to the outlet of the shaped muffle tube, is used to anneal the drawn optical fiber.

2. The graphite furnace according to claim 1, characterized in that: The convex bottom plate includes a protruding connector and a bottom plate; the protruding connector is annular, and its outer periphery is sealed to the lower opening of the furnace body, and the bottom plate is connected to the protruding connector.

3. The graphite furnace according to claim 2, characterized in that: The protruding connector has a first through hole at its center; the base plate is embedded and fixed in the first through hole, and the base plate has a second through hole at its center that is coaxial with the first through hole. The two through holes together form a continuous heat flow channel.

4. A graphite furnace according to claim 2, characterized in that: The protruding connector is provided with several threaded blind holes, and the bolt passes through the threaded blind holes to fix the lower end opening of the furnace body.

5. A graphite furnace according to claim 1, characterized in that: The height of the protruding connector protruding from the lower opening of the furnace body is 10 mm ± 1 mm.

6. A graphite furnace according to claim 1, characterized in that: The convex base plate is made of TC4 titanium alloy.

7. A graphite furnace according to claim 1, characterized in that: The induction coil is a 265 type coil with a wire diameter of 8mm and a turn spacing of 3mm.

8. A graphite furnace according to claim 7, characterized in that: The induction coil has 10 turns.

9. A graphite furnace according to claim 1, characterized in that: The annealing tube is fitted with a protective sleeve on its outer side.

10. An optimized method for reducing the power consumption of a graphite furnace, characterized in that, include: S1: A convex bottom plate is provided at the lower opening of the furnace body, such that the convex connecting piece of the convex bottom plate protrudes out of the lower opening of the furnace body by 10 mm ± 1 mm. S2: Synchronously incrementally match the height of the graphite central tube so that the graphite central tube abuts against the protruding connector; S3: Increase the number of turns of the induction coil to 10 and move the entire induction coil down by 8-10 mm, so that the center of the hot zone moves down and forms a composite hot field with the arc-shaped reflective surface of the shaped muffle tube.

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