Industrial electric heating furnaces – Induction furnace device – Coreless
Reexamination Certificate
2003-01-06
2004-07-27
Hoang, Tu Ba (Department: 3742)
Industrial electric heating furnaces
Induction furnace device
Coreless
C373S153000
Reexamination Certificate
active
06768766
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to induction furnaces and more particularly to the upper rings used in such furnaces.
DESCRIPTION OF THE PRIOR ART
An induction furnace employs electromagnetic energy to induce electrical currents to flow within a charge of metal or metal alloy. The electrical resistance of the metal produces heat as a natural consequence of the induced currents flowing in the metal. The combination of applied electrical power and frequency can be chosen to create sufficient heat within the metal to cause it to melt. The molten metal can then be poured into molds or otherwise used to produce a wide variety of metal products.
Referring now to
FIG. 1
there is shown the cross-section of a traditional induction furnace
10
. The basic elements of induction furnace
10
include an electromagnetic induction coil
12
, a crucible or vessel
14
having a lining
28
of refractory material and a structure
16
for supporting the induction coil and vessel. The induction coil
12
comprises an electrical conductor of sufficient size and current capacity to produce the magnitude of magnetic flux necessary to induce large currents in the metal charge. The magnetic flux represents the lines of force of a magnetic field. The magnetic field emanates from the furnace coil and penetrates the charge material inside the crucible
14
, causing induced current to flow in the charge resulting in the generation of heat culminating in the melting of the charge material.
Magnetic yokes
18
are placed at periodic intervals around the outside of the induction coil
12
and are pressed inward by means of clamping bolts
20
to hold the induction coil
12
in place. The yokes
18
provide radial support to the coil
12
, the crucible
14
, and the charge material contained therein. In addition, the yokes
18
prevent the stray flux surrounding the outside of the coil from entering the frame
16
of the furnace and causing unwanted heating of the structure. A further function of yokes
18
is to minimize exposure of operating personnel to stray magnetic fields in order to comply with applicable health and safety rules.
The coil
12
is held in place axially by means of concrete castings
22
and
24
in the form of a ring that are typically cast in place after the coil
12
and yokes
22
are installed. As is well known, lower ring
24
of traditional furnace
10
has straight outer walls. Also shown in
FIG. 1
are the cover
25
, the quick lining release push-out plug
26
, Ground electrodes
27
and spout
29
.
In some of the larger traditional furnaces there is axial compression on the coil
12
from the bottom only of those furnaces. Since in those furnaces the upper end of the coil
12
does not receive direct axial compression the longevity of the coil may be compromised under certain severe conditions of operation.
Although traditional furnace
10
has proven to be durable it may be necessary during the life of the furnace to change coil
12
or the cast in place upper ring
22
from time to time at an interval from 6 months to several years depending on severity of service. That change is a time consuming and lengthy procedure usually requiring at least several days and for larger furnaces up to two weeks. During that time period there is a loss of production from the furnace. Therefore it is desirable to reduce the amount of time and labor and thus the cost of replacing the coil or the upper ring and also allow a future replacement of either or both elements to be easily made. As can be appreciated a reduction in the amount of time to replace the coil or upper ring can add to production from the furnace. The structure and method of the present invention provides these benefits as well as benefits in the construction of new furnaces.
SUMMARY OF THE INVENTION
A method for replacing an upper ring casted on an induction furnace comprising replacing the upper ring casted on the furnace with a holder having a cured ring that is cast as one piece in the holder off of the furnace.
A method for replacing an upper ring casted on an induction furnace comprising:
a) casting an upper ring as one piece in a holder off of the furnace; and
b) replacing the upper ring casted on the furnace with the holder having therein the one piece upper ring after the one piece upper ring is cured.
A method for replacing an upper ring of an induction furnace comprising:
a) removing the upper ring;
b) casting an upper ring as one piece in a holder off of the furnace; and
c) placing the holder having the one piece upper ring therein on the furnace after the one piece upper ring is cured.
A method for replacing components in an induction furnace, the furnace comprising an upper ring, an induction coil, yokes, a lower ring and a frame, the method comprising:
a) removing the upper ring, the lower ring, the induction coil and the yokes from the furnace;
b) casting an upper ring as one piece in a holder off of the furnace;
c) returning the yokes to the furnace;
d) replacing the removed induction coil with an induction coil modified to include cooling turns at the top of the induction coil;
e) tightening the yokes while ensuring that the modified coil remains centered and plumb within the furnace frame;
f) casting a new lower ring on the furnace; and
g) installing the holder on the furnace after the one piece upper ring is cured.
An induction furnace comprising:
a) a crucible having a refractory lining for holding a charge of metal or a metal alloy;
b) an electromagnetic induction coil surrounding the crucible; and
c) upper and lower castable rings for holding the coil axially, the lower ring cast on the furnace and the upper ring in a holder and cast as one piece in the holder off of the furnace.
An upper ring for an induction furnace that comprises a holder in which the ring is cast in one piece, the holder for mounting the cast one piece upper ring on the furnace.
REFERENCES:
patent: 3944715 (1976-03-01), Hegewaldt et al.
patent: 4622679 (1986-11-01), Voss
patent: 5425048 (1995-06-01), Heine et al.
ABB Inc.
Hoang Tu Ba
Rickin Michael M.
LandOfFree
Precast one piece upper castable ring for induction furnaces does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Precast one piece upper castable ring for induction furnaces, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Precast one piece upper castable ring for induction furnaces will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3249008