BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
FIG. 1 is a graph shows a heating curve of an optical fiber plotting temperature against time for a method according to one embodiment of the invention, and illustrating the point where the change in heating speed occurs, as discussed above in the Brief Summary of the Invention section;
FIG. 2 is a schematic illustration of a device according to one embodiment of the invention;
FIG. 3 is a schematic illustration of a mechanical vibration option for the device;
FIGS. 4
a to 4c are schematic illustrations of the device according to different embodiments of the invention, each with detector;
FIGS. 5
a to 5d are schematic cross-sections of various embodiments of a fiber with a cover for the device; and
FIG. 6 is a detailed illustration of the fiber in cross-section.
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1 the temperature/time course is illustrated for the immersion of an optical fiber in a molten steel bath according to the method of the invention. The immersion speed of the quartz glass fiber with cover in the molten steel bath is equal to its destruction speed (erosion speed), so that the erosion face is quasi stationary in the molten metal bath. This speed corresponds to the critical speed, so that the optical fiber on its destruction face has reached the bath temperature.
Inside its covering the quartz glass fiber itself has only a very small increase in temperature over a long period of time. At a particular point in time its cover is suddenly removed, so that its temperature increases in a short time very steeply until it reaches the equilibrium temperature in the molten steel bath.
In FIG. 2 a melting tub 1 with a molten steel bath 2 is illustrated. An optical fiber arrangement 3 is immersed in this bath. The optical fiber arrangement 3 has, above the molten metal bath, an outer covering 4, which serves for easier propulsion by a propulsion device 5. At the end of the covering 4 facing the molten steel bath 2 a vibrator 6 is arranged, which beats on the covering 4 at short intervals, so that the cover of the quartz glass fiber is suddenly destroyed by the vibration generated, as soon as it has reached a predetermined temperature. At this point the temperature of the outer steel cover is already very high, the powder arranged between the quartz glass fiber and the outer steel cover or the gas contained in the intermediate layer has greatly expanded and, assisted by the mechanical effect of the vibrator 6, explodes the steel cover which is under thermo-mechanical stresses in any case. As a result, the quartz glass fiber is immediately exposed to the temperature of the molten steel bath, so that it heats up extremely quickly to the equilibrium temperature. The intermediate layer is formed of silicon dioxide powder or aluminium oxide powder.
FIG. 3 shows an optical fiber arrangement 3 with a cover, which has on its outside irregularities arranged in succession in the longitudinal direction. The optical fiber arrangement 3 is guided by a guide sleeve 7, which has inside it a support element 8, along which the optical fiber arrangement 3 is guided. On the side of the optical fiber arrangement 3 opposite the support element 8 an edge of the guide sleeve 7 is tangent-bent inwardly, so that at this point it forms an obstacle 9. This obstacle 9 engages in the irregularities of the optical fiber cover, so that the optical fiber arrangement 3 is constantly vibrated during its advance movement.
FIG. 4
a shows an optical fiber arrangement 3, in which the fiber 10, a quartz glass fiber, is surrounded by a steel tube 11. Inside the steel tube 11 is arranged an intermediate layer 12 made of aluminium oxide powder. The quartz glass fiber 10 is connected to a detector 13 at its end facing away from the immersion end of the optical fiber.
In FIG. 4b a similar arrangement is illustrated, and here the quartz glass fiber 10 is surrounded by a metal sleeve 14. Cooling gas can be conducted through the metal sleeve 14, which is guided out of the steel tube 11 at the detector-side end of the optical fiber arrangement 3, so that the quartz glass fiber 10 is additionally cooled.
FIG. 4
c shows an arrangement, likewise similar to FIG. 4a, of an optical fiber 3. The intermediate space between the steel tube 11 and the quartz glass fiber 10 is divided into a plurality of chambers with the aid of cardboard discs 15 arranged perpendicular to the optical fiber 10. The cardboard discs 15 serve on the one hand to stabilize the intermediate layer 12. They stabilize, in particular, the powder of the intermediate layer 12 during the destruction of the optical fiber arrangement 3, running in the longitudinal direction. On the other hand, during the burning of the cardboard discs 15, taking place because of the heating, an additional discontinuity/disruption is generated, which contributes to exposing the quartz glass fiber 10 quickly to the molten metal bath, so that it heats up very quickly after the destruction of the cover.
In FIGS. 5a to 5d several options are illustrated for stabilizing the quartz glass fiber 10 in the center of the cover of the optical fiber arrangement 3. According to FIG. 5a, the steel tube 11 is bent in such a way that it forms in one piece a concentrically arranged inner tube 16, which is connected to the outer steel tube 11 by a web 17 running along the cover. The outer steel tube 11 is welded together at a seam point 18 and has a wall thickness of approximately 0.5 mm. The quartz glass fiber 10 is arranged in the inner tube 16.
In the embodiment according to FIG. 5b the quartz glass fiber 10 is arranged centrally in the material of the intermediate layer 12.
FIG. 5
c shows a further embodiment of the optical fiber arrangement 3, similar to FIG. 5a. Here, though, the steel tube 11 is composed of two halves, in each case jointly forming two webs 17, by which the quartz glass fiber 10 is centrally locked.
The embodiment according to FIG. 5d is similarly constructed. It additionally has a second outer steel tube 19, which holds together the steel tube 11 formed from two shells. The wall of the two steel tubes 11, 19 can be reduced correspondingly in respect of the other embodiments and amounts in each case to approximately 0.25 mm. A single welding at the seam point 20 is required.
FIG. 6 shows a fiber cross-section in detail. The quartz glass fiber 10 is surrounded at a minimal distance by a steel casing 21, so that different expansions of the two materials on heating are possible, and the quartz glass fiber 10 is nevertheless stabilized. Between the steel casing 21 and the steel tube 11 is arranged an intermediate layer 12 made of aluminium oxide particles. The steel tube 11 is rolled from a metal sheet and closed by a fold 23.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
Patent Application
20070268477
