System for insulating an induction vacuum furnace and method of making same

Abstract

A system and method for insulating an induction vacuum furnace is disclosed. An induction furnace for heating a workpiece includes a chamber, an insulation cylinder positioned within the chamber, and an induction coil positioned to surround at least a portion of the insulation cylinder. A susceptor is positioned within the insulation cylinder and inductively heated by the induction coil when a current is provided to the induction coil. An insulating jacket assembly including one of a carbide material and a refractory metal is positioned in a space between the insulating cylinder and the susceptor.

What is claimed is: 
     
         1 . An induction furnace for heating a workpiece, the induction furnace comprising:
 a chamber;   an insulation cylinder positioned within the chamber;   an induction coil positioned to surround at least a portion of the insulation cylinder;   a susceptor positioned within the insulation cylinder, the susceptor being inductively heated by the induction coil when a current is provided to the induction coil; and   an insulating jacket assembly comprising one of a carbide material and a refractory metal, the insulating jacket assembly positioned in a space between the insulating cylinder and the susceptor.   
     
     
         2 . The induction furnace of  claim 1  wherein the insulating jacket assembly is sized to substantially surround the susceptor. 
     
     
         3 . The induction furnace of  claim 1  wherein the insulating jacket assembly further comprises a plurality of layers. 
     
     
         4 . The induction furnace of  claim 3  wherein a first portion of the plurality of insulating layers surrounds a side wall of the susceptor. 
     
     
         5 . The induction furnace of  claim 3  wherein a second portion of the plurality of insulating layers is positioned above a top surface of the susceptor; and
 wherein a third portion of the plurality of insulating layers is positioned below a bottom surface of the susceptor. 
 
     
     
         6 . The induction furnace of  claim 1  further comprising:
 a first graphite plate; and 
 a second graphite plate; and
 wherein the first and second graphite plates are positioned to retain the insulating jacket assembly against the susceptor. 
 
 
     
     
         7 . The induction furnace of  claim 1  wherein the insulating jacket assembly comprises a graphite felt. 
     
     
         8 . The induction furnace of  claim 1  wherein the insulating jacket assembly comprises a material that is transparent to induction. 
     
     
         9 . The induction furnace of  claim 1  further comprising a linear actuator coupled to the chamber and a bottom cover of the insulation cylinder; and
 wherein the linear actuator is configured to translate the bottom cover between a raised position, wherein the workpiece is positioned in a heating zone of the induction furnace within the susceptor, and a lowered position, wherein the workpiece is positioned in a cooling zone of the induction furnace, outside of the susceptor. 
 
     
     
         10 . The induction furnace of  claim 9  further comprising a bellows system coupled to the bottom surface of the insulation cylinder;
 wherein the bellows system has an interior volume fluidly coupled to an interior volume of the chamber; and 
 wherein the bellows system is configured to maintain a hermetic seal in the chamber from an ambient environment during movement of the bottom cover between the raised and lowered positions. 
 
     
     
         11 . An induction furnace comprising:
 a chamber having a susceptor positioned therein, wherein an interior volume of the susceptor defines a zone within the chamber for heating a workpiece;   an insulation package comprising:
 a fused quartz cylinder positioned around the susceptor; and 
 a graphite jacket positioned between the fused quartz cylinder and the susceptor; and 
   a coil surrounding the insulation package and configured to inductively heat the interior volume of the susceptor when a current is provided to the induction coil.   
     
     
         12 . The induction furnace of  claim 11  wherein the graphite jacket comprises a plurality of layers of graphite felt. 
     
     
         13 . The induction furnace of  claim 11  wherein a first portion of the graphite jacket surrounds a side wall of the susceptor;
 wherein a second portion of the graphite jacket covers a top cover of the susceptor; and 
 wherein a third portion of the graphite jacket covers a bottom cover of the susceptor. 
 
     
     
         14 . The induction furnace of  claim 11  further comprising:
 a first graphite plate positioned between the fused quartz cylinder and a top surface of the susceptor; and 
 a second graphite plate positioned between the fused quartz cylinder and a bottom surface of the susceptor. 
 
     
     
         15 . The induction furnace of  claim 11  further comprising:
 a linear actuator coupled to a bottom cover of the fused quartz cylinder and configured to move the bottom cover in vertical manner between a raised position and a lowered position; and 
 a vacuum-sealed bellows system configured to maintain a vacuum pressure in the chamber during movement of the bottom cover of the fused quartz cylinder between the raised position and the lowered position by way of the linear actuator. 
 
     
     
         16 . A method of making an induction furnace comprising:
 providing a vacuum chamber;   coupling an insulation cylinder within the vacuum chamber;   coupling an induction coil to surround at least a portion of the insulation cylinder;   coupling a susceptor within the insulation cylinder; and   encapsulating the susceptor with an insulating jacket, wherein the insulating jacket comprises one of a carbide material and a refractory metal.   
     
     
         17 . The method of  claim 16  further comprising positioning a pair of graphite plates at respective top and bottom exterior surfaces of the susceptor. 
     
     
         18 . The method of  claim 16  wherein encapsulating the susceptor with an insulating jacket comprises covering exterior surfaces of the susceptor with a plurality of layers of graphite felt. 
     
     
         19 . The method of  claim 16  further comprising:
 encapsulating a side wall of the susceptor with a first portion of the insulating jacket; 
 encapsulating a top surface of the susceptor with a second portion of the insulating jacket; and 
 encapsulating a bottom surface of the susceptor with a third portion of the insulating jacket. 
 
     
     
         20 . The method of  claim 16  further comprising:
 coupling a bellows system to a bottom surface of the insulation cylinder, the bellows system having an interior volume fluidly coupled to an interior volume of the chamber; 
 coupling a linear actuator to the bellows system; and 
 configuring the linear actuator to selectively translate the bottom cover of the insulation cylinder between open and closed positions.