Induction heating

Details Induction heating Induction heating

2000-09-26

2002-06-04

Hoang, Tu Ba (Department: 3742)

Industrial electric heating furnaces

Induction furnace device

Coreless

C373S154000

Reexamination Certificate

active

06400749

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to induction heating, and in particular to a coreless induction furnace or induction heated channel furnace and a lining material therefor.
2. Description of the Prior Art
A coreless induction furnace usually comprises a vessel having a refractory crucible inside a water cooled induction coil. The innerface of the induction coil is usually covered by a thin layer of refractory plaster which is called the coil grout. There is a need to interpose a layer between the coil grout and the refractory crucible to provide a slip plane between these two surfaces. FR-A-2101903 discloses an induction furnace having a slip plane comprising a layer of spun glass fiber.
BRIEF SUMMARY OF THE INVENTION
According to the invention in one aspect there is provided an induction furnace comprising a vessel comprising a refractory crucible within a cooled induction coil, slip plane material and supporting material being present between the crucible and the coil, characterized in that the slip plane material comprises a flexible mica paper or sheet.
In a much preferred feature the slip plane material and the supporting material are present as a laminate.
Preferably the supporting material therefor is a glass fiber fabric. Preferably the glass fabric has a density of between about 500 g/m
2
and about 1500 g/m
2
, preferably 800 to 1350 g/m
2
and a thickness of between 0.8 to about 2.5 mm. preferably 1.4 mm. to 2.2 mm. Preferably the glass fiber fabric is woven.
In another aspect the invention provides a method of preparing a coreless induction furnace comprising a vessel having a refractory crucible surrounded by a cooled induction coil, the method comprising locating a slip plane material L
1
and other material (L
2
) in between, characterized by interposing a layer of flexible mica or sheet as the slip plane material (L
1
) between the refractory crucible wall (
2
) and the surrounding cooled inducting coil.
In yet another aspect the invention provides for use in the lining of an induction furnace as defined, a laminate comprising a layer of flexible mica paper or sheet and supporting layer of glass fiber fabric. The two layers being held together by an inorganic binder.


REFERENCES:
patent: 3708600 (1973-01-01), Nickel et al.
patent: 4675879 (1987-06-01), Meredith
patent: 5280495 (1994-01-01), Havas et al.
patent: 5416795 (1995-05-01), Kaniuk et al.
patent: 5781581 (1998-07-01), Fishman et al.
patent: 6148018 (2000-11-01), Garcia et al.
patent: 408293 (1966-12-01), None
patent: 160384 (1985-11-01), None
patent: 801516 (1997-10-01), None
patent: 2101903 (1972-03-01), None
patent: WO 97/18690 (1997-05-01), None

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