| 摘要 |
PURPOSE:To prevent consumption owing to oxidation of a heating element by diving the shielding cylinders covering the part of a porous glass sintered body having been made transparent to upper and lower to form a clearance, heating the sintered body from here and feeding the nonoxidative gas existing in the surroundings into the shielding cylinders. CONSTITUTION:An annular heating element 14 is placed within a hermetic vessel 12 into which a nonoxidative gas is fed. A bar-shaped porous glass sintered body 15 is passed in its inside. This sintered body 15 is connected to the bottom end of a supporting bar 18 and is moved upward while being slewed so that its top end is projected from the hermetic vessel. On ther other hand, the shielding cylinders 16, 17 divided to upper and lower are so provided as to cover the sintered body 15 and are fixed to the hermetic vessel 12. Through the clearance between these upper and lower shielding cylinders 16, 17, the nonoxidative gas existing around the heating element 14 is continously fed into the shielding cylinders 16, 17 and at the same time the sintered body is heated thereby. Because of this, the heating element is prevented from being consumed by oxidation. |
