Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
The present invention relates to electric furnace heaters, and more
particularly, to an electric heater assembly for installation in the base
of such a furnace.
Problems associated with providing a heat source in the base of an
electric furnace are longstanding. Typically, once a furnace is constructed,
accessibility of the heat source is, at best, achieved with much difficulty.
The problem is compounded by the failing, in service, of such heaters, often
inexplicably. Often times, however, heater failure results from falling
materials, sometimes parts being processed, and other times debris,
impacting the heater unit.
It is,therefore, desirable to provide an electric resistant heater
assembly for use in the base of an electric furnace wherein protection is
provided the heater against materials falling from above.
Accordingly, it is an object of the present invention to provide an
electric heater assembly, a module, for use in the base of an electrically
heated furr~ace, the assembly being free-standing and including heater support
structure providing means for shielding the heating element from falling
debris .
Summarv of the Invention
In accordance with the present invention, there is provided a free-
standing, electric heater assembly for removable installation in the base
of an electric furnace below the level of materials placed therein for processing.
An electric resistance heating element and refractory means for supporting
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the heating element are provided. The refractory means includes means
for shielding the heating element from material which may fall from above
in the furnace.
Brief Description of the Drawing
The preferred embodiment of the invention is shown in the accompanying
drawing in which:
FIG. 1 is an end view of the heater assembly generally as seen along
line 1-1 in FIG. 2;
FIG. 2 is a side elevation view of the heater assembly generally as seen
along line 2-2 in FIG. 1 and with the heater assembly mounted in a furnace; and
FIG. 3 shows, in perspective, a cutaway view of an electric furnace
of the roller hearth type wherein the free-standing heater assembly is removablyinstalled in the base portion.
Description of the Preferred Embodiment
Referring to FIG. 1, there is shown a free-standing electric heater
assembly 10 in accordance with the present invention. Included is an electric
resistance heating element 20 and refractory means for supporting the heating
element in the form of an I-beam 30 cast of a refractory material. I-beam 30
includes a web section 32 and a pair of flanges 34 and 36. A plurality of
ceramic rods 38 are provided protruding from the web 32 and are spaced
apart along the length of the I-beam as shown in FIG. 2 for receiving the
heating element 20. Flange 34 of the refractory I-beam serves as the base
for the assembly and provides stability while nange 36 serves as the means for
shielding the heating element from material which may fall from above in
the furnace.
7~
In the embodiment shown, ceramic rods 38 are assembled thru holes
formed in the I-beam web 32 such that the ceramic rods 38 protrude an equal
distance from either side of the web. This allows for the heating element 20
to be mounted upon both sides of the refractory I-beam web.
In the embodiment shown, the heating element 20 is assembled upon
the ceramic rods 38 in serpentine fashion. The free ends of the heating
element are connected to suitable electrical connectors for connection to a
source of electrical energy (FIG. 3).
The arrangement shown has been constructed and operated satisfactorily.
The heating element 20 was formed of nickel-chromium alloy (tradename
Nichrome) having a thickness of . 045 inches and a width of 11/2 inches and
provided an overall resistance of 1 ohm. The refractory I-beam 30 was cast
using a form provided with tubes therethru to allow it to be cast in its finished
shape complete with the holes to carry the ceramic rod heating element
supports 38. Refractory Moldit D, a castable refractory obtained from
Combustion Engineering Inc. Valley Forge, Pa. was used for the casting.
After filling the form with the casting material, the I-beam casting is allowed
to dry for 24 hours and then removed from the form. The ceramic rods 38
are then cemented into position using the same castable refractory as a
cement. The casting is placed in a furnace at 500 degress F. for 24 hours,
after which the temperature is raised 100 degrees F. every hour until it
reaches 2, 000 degrees F. The cured refractory I-beam then has a compressive
strength of 20 tons per square inch; such allows the second flange 30 and the
I-beam generally to serve as a load-bearing structure.
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.
In thc cmbodimcnt shown, the I-beam flanges arc 8 inchcs wide; the
~ I-beam structure bein6 7 inchcs high and 54 inches long. Thc wcb 32 i8
- two inches widc; thc widest part of the flange is 1 inch widc and thc outcrmost
e3ctremities of thc nanges are 3/4 inch wide. The holcs for receiving thc ceramic
rods 38 are sized to accept 3/4 inch diameter ceramic rods having a length
of 7 3/4 inches, 19 holes being provided spaced apart equally at 2 1/2 inches.
Such an arrangement provides satisfactory operation including suitable
protection to the heating element 20 from foreign materials, including material~being processed, which might otherwise fall down upon, and damage, the
heating element.
Referring now to FIG. 3, there is shown a cutaway view of a portion of
an electric roller hearth furnace 50 wherein the free-standing electric heater
as6embly 10 of the present invention i5 incorporated for removable installation
in the base thereof. Furnace 50 includes a pair of insulated sidewalls, one
of which is shown at 52 and an insulating base 56. A plurality of rollers 58
are provided upon which materials to be processed in the furnace are placed.
The rollers 58 may be provided with drive means for passing materials through
the furnace at some particuiar velocity. One of the sidewalls 52 is provided
with an opening through which heater assembly 10 may be inserted and removed
for examination or replacement. A hole-cover plate 60 of some suitable in-
sulating material is provided for closing the opening after the heater assembly
0 i6 installed. Cover-plate 60 is provided with a pair of electrical conductors
62 passing therethrough for connection to the free ends of heating element 20
and to a ~urce of electrical energy.
It i~ contcmplated that heater assembly 10 mag be installed in a standard
~urnace without rollers. With such an arrangement, materials to be processed
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in the furnace may be placed upon and supported by the refractory I-beam 30,
While an embodiment and application of this ;nvention has been shown and
described, it will be apparent to those skilled in the art that modifications
are possible without departing from the inventive concepts herein described.
For example, it is contemplated that the refractory I-beam structure of this
embodiment could be suitably replaced by a structure having a cross section
triangular in shape and provided with a top cover plate, the ceramic rods
being passed through and protruding from the base section. Likewise, the
structure could be formed of a generally T-shaped cross section wherein
the base portion is generally rectangular in cross section and is covered with
a top cover plate. Both of these configurations, and others too, offer stabilityto the assembly as well as protection to the-heating element from falling
debris. The invention therefore is not to be restricted except as is necessary
by the prior art and the spirit of the appended claims.
