US 4,547,644 A · Apparatus for heating a preform from which lightguide fiber is drawn

Abstract

An induction furnace (60) for reflowing a portion of an optical preform (12) in order to draw a lightguide fiber (11) therefrom includes a tubular susceptor (80) which is disposed centrally within a beaker (75) and a sleeve (82) which is disposed concentrically about the susceptor. The sleeve is spaced from the susceptor and is surrounded by insulating grain (83). A high frequency coil (84) is energized to couple its electromagnetic field to the susceptor to heat and reflow a portion of the preform. The movement of contaminating particles of the insulating grain into the interior of the susceptor is prevented substantially by annular, felt-like discs (91, 105) at the bottom and top of the beaker. The discs collect particulates which move downwardly and upwardly and because of their compliant engagement with the beaker and with the sleeve, they provide seals at those interfaces. The discs also are effective to prevent inadvertent lateral movement of the sleeve to maintain the concentricity of the sleeve and the susceptor. The top of the furnace is provided with a cap (93) which is supported by the susceptor that extends into a stepped opening of the cap.

Claims15

Dependent claims

A furnace for heating a preform in order to draw lightguide fiber therefrom, said furnace comprising:

a container which includes a sidewall and a base having an opening therethrough;
a tubular element having a bore into which the preform extends, said tubular element being supported on said base in alignment with said opening and enclosed by said sidewall;
means for causing the temperature of an optical preform which extends into said bore to be increased to facilitate the drawing of lightguide fiber therefrom;
insulating means disposed between said sidewall of said container and said tubular element;
and
sealing means engaging said insulating means and extending across said base between and in compliant engagement with said container and said tubular element for preventing substantially the movement of contaminating particulates from said insulating means into the bore and for preventing unintended lateral movement of the tubular element.

3 more elements

An induction heating furnace for heating an optical preform, said furnace comprising:

a housing which includes a base having an opening formed therethrough;
a beaker which is disposed within said housing, said beaker including a base which is in engagement with said base of said housing and a sidewall, said base of said beaker having a stepped opening which extends centrally therethrough in alignment with the opening through said base and which provides an annular ledge;
a tubular susceptor which is disposed in said beaker and into which a portion of the preform extends, said susceptor having a lower peripheral surface being disposed in engagement with said ledge of said stepped opening of said beaker base;
a sleeve which is disposed concentrically about said susceptor and spaced therefrom, said sleeve being supported in engagement with said base of said beaker, and said beaker providing an annulus between its sidewall and said sleeve;
insulating grain surrounding said sleeve and disposed within said annulus between said sleeve and said beaker sidewall;
mean for heating said susceptor;
and
sealing means disposed between said insulating grain and said base of said beaker within said beaker and which is in compliant engagement with said beaker sidewall and said sleeve for preventing the movement of insulating grain into the interior of said susceptor and for maintaining the sleeve disposed concentrically about said susceptor.

5 more elements

Dependencies are inferred from the claim text.

Apparatus for heating a preform from which lightguide fiber is drawn

Life of this patent

Apparatus for heating a preform from which lightguide fiber is drawn

Life of this patent

Abstract

Claims15