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Патент USA US2588142

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arch 4, i952
J. l.. MGFARLAND ET AL
2,588,141
CONTINUOUS TYPE FURNACE
Filed Sept. 22, 1948
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Inventor:
«James L3. McFarland
NOT-‘ma? B.Jovwes
Their Att Orr/1 ey.
2,588,141
Patented Mar. 4, 1952
UNITED STATES> PATENT oFFlcE
2,588,141
l
CONTINUOUS TYPE FURNACE
James L. McFarland, Schenectady, and Norman
B. Jones, Ballston Lake, N. Y., assignors to
General Electric Company, a corporation of
New York
Application September 22, 1948, Serial No. 50,506
2 Claims. (Cl. 263-8)
1
2
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Work pieces 4 to be heated. The rollers I are 'Y
driven in synchronism by a suitable driving
Our invention relates to furnaces, particularly
to high temperature furnaces of the type adapted
for continuous operation including roller hearth
means such as electric motor 5, best seen in Fig. 2, '
furnaces and the chain conveyor type. Our in
vention has for its object to provide an improved
furnace and furnace conveying system which fur
nishes uniform heating and economical opera
tion with a reasonable first cost.
Heretofore, roller hearth furnaces have been
limited to a practical width of a few feet, when
used for high temperature Work, because of the
through a suitable driving mechanism such as
continuous chain 6 and sprockets 1, which Aare
best seen in Fig. 3. In this particular construc
tion, the corresponding rollers on the two rows
of rollers are coupled together by means of a
suitable external interconnecting shaft and cou
pling assembly 8 so that the left row of rollers in
"Fig. 2 is driven from and in synchronism with
the right row which, in turn, is driven by the _
adverse effect of high temperatures on the ‘physi
motor and chain and sprocket mechanism.
cal strength of the rolls. Accordingly, it is a
In the operation of this furnace, the elevated
further object of our invention to provide roller
hearth type furnaces of much greater width than 15 lcarriers or fixtures 3 supporting the Work to be
present designs permit.
heated 4 are brought to the furnace by a suitable
conveyor 9. The door IU is opened to admit the
supporting ñxtures and work to the furnace and
they pass through the furnace from left to _right
temperatures because of the necessity for keep
ing the conveyor chain cooler than the furnace 20.. in Fig. 1. In zone l, the work is preheated, *for
proper and because of the escape of heat through 1 example, to approximately 1000° F. In zone 2,
the final heating takes'place and the tempera
necessary openings in the furnace insulation. It
ture of the work is raised, for example, to ap
is therefore another object of our invention to
proximately 1725° F. In zone 3 of the furnace,
provide a chain conveyor type furnace, especially
one of large physical size, which can be operated 2,5.. the work is cooled, for example, to approximately
at high temperatures with uniform results.
1200° F. Door H is then opened and the work and
the supporting fixtures are discharged onto a suit
In carrying out our invention in one form we '
provide a continuous roller hearth type electric
able conveyor í2 which removes them from the
furnace with two parallel rows of rollers extend
furnace. The work can be allowed to cool natu
ing the full length of the furnace. These rollers
rally
after it has been removed from the furnace '
30
Again, conventional chain conveyor furnaces do
not provide uniform heating when used at high
support suitable elevated carrying devices which,
or it can be cooled more rapidly by an air blast
or ,other suitable means (not shown) as it is be
ing removed from the furnace.
in turn, support the work to be heated. The
rollers are recessed in the floor ofthe furnace,
and the recesses are completely insulated so that
there is no large heat loss. While these recesses
are maintained at practically full furnace tem
perature, the rollers -are comparatively short and,
35
This furnace is heated electrically by electric
heaters I3 distributed throughout the furnace.
However, our invention is equally applicable to
furnaces heated by other conventional means,
therefore, can be designed to withstand high tem
such as natural or manufactured gas or oil. '
peratures without exceeding the stress limitations
Furthermore, While our improved furnace has
of the metal of which they are made. 'I'he rollers 40 been illustrated as employing two complete sets
are driven in synchronism by a suitable external
orv rows of rollers, any desired numberv of such
means.
.
'
For a more complete understanding of our in
vention, reference should be had to the attached
sets or rows may be employed. By- theuse of a
suitable number of rows of rollers, furnaces can
be made any desired width by the use of our ín
drawing which shows in Fig. 1 a side view of one 45 vention. Heretofore, roller hearth furnaces have
form of our invention; Fig. 2 is a sectional view
been limited to a width of approximately 81/2 feet
taken along the line 2-2 of Fig. 1; and Fig. 3
when constructed for operation at 1650D F. be
is a partial detailed sectional View taken along
cause of the adverse effect of such a high tem
the line 3-3 of Fig. 2.
perature on the physical strength of the rolls,
Referring to Fig. 1 of the drawing, the rollers l 50 this width being the over-all outside dimension;
can be seen extending thev full length of the fur
the corresponding inside Wall to wall width in the
heating chamber is approximately 6 feet. At
2050° F., the present practical maximum outside
The rollers l support the elevated carrying de
width is approximately 5 feet, which gives an in
vices or fixtures 3 which, in turn, support the 55 side Working width of approximately 30 inches.
nace; Fig. 2 shows the relation of the rollers to
the insulated recesses 2 in the furnace floor.
2,588,141
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means for providing an artificial non-oxidizing
reducing atmosphere utilizing such gases as hy
drogen, or a mixture of hydrogen and nitrogen,
or atmosphere convertor gas which is made by
One modification of our invention relates to
the use of rollers. similar to those already .de
scribed, in completely insulated recesses in the
floor of the furnace to support one or more chain
conveyors. These chain conveyors are conven 5 burning suitable manufactured or natural gas
with a controlled deficiency of air. Hign tem
perature furnaces are sometimes used without
artificial atmosphei'e, however, for some kinds of
material. Our invention is suitable for applica
tion to furnaces with or without artificial atmos
tional in form except that they are made of special
alloy steel to withstand full furnace tempera
ture. They have dogs or other prolecting mem
bers on them which project above the furnace
floor and propel the work to be heated along the
phere.
floor of the furnace from the entrance to the
While we have described one preferred em
bodiment'of our invention along with one modifi
cation, many other modifications will occur to
exit. This arrangement is applicable primarily
to large pipes and other similar objects which
will roll tlirough the furnace when pushed by
the dogs on the conveyor chains. Alternatively, 15 those skilled in the- art and it should, therefore,
be understood that we intend by the appended
if the material to be heated is not suitable for
claims'to cover alll such modifications which fall
rolling, the conveyor chains can be made of such
withinthe true spirit and scope of our invention.
dimensions that they support the weight of the
What we claim as new and desire to secure by
work 1n the furnace While they, in turn, are sup
Patent of the United States is:
ported by the recessed rollers.
y
20 Letters
1`. A horizontally disposed furnace of the type
Tile use oi sucli a cilaiii conveyor or conveyors
adapted for continuous conveyor operation hav
operating at ruil furnace temperature is made
ing a plurality of parallel insulated recesses in
practical oy the use ol the recessed supporting
the ñoor of the furnace heating chamber and
rollers of our invention. These rollers greatly
reduce the il'lctloil oil tile chalii or ciiallls wl'ilcll, 25 extending longitudinally througii said furnace,
a plurality of rollers extending transversely
in turll, i‘educes trie size ol chains required to
through one of said recesses, an equal number of
rollers extending transversely through each of
is required to withstand nign tempera
the other recesses, means supported by said roll
Conventional chain conveyor type iur
where the chains are supported in metal 30 ers for propelling work through the furnace,
means external to said heating chamber for con
somewhat below the 1100i` oi the furnace,
witilin practical limits lor the special alloy steel
wllich
tures.
naces,
guides
necting together corresponding rollers in sep
are not practical for use at high temperatures
in large installations. The chains must be of
arate recesses, and means external to said heat
ing chamber for driving said rollers irl syncnro
and the large friction load, caused by tile weight 35 nism to actuate said work propelling means.
2. A horizontally disposed furnace adaptable
or tile chains themselves in the metal guides, in
for continuous conveyor operation having a plu
addition to the work being propelled through the
rality of parallel insulated recesses in the floor of
furnace, makes the chains so large that the cost
the furnaceV heating chamber extending longi
is prohibitive.
Furthermore, on conventional chain conveyor 40 tudinally through said furnace, a plurality of
rollers extending transversely through one of
furnaces there usually are slots cut in the floor
said recesses, an' approximately equal nuinoer of
insulation t0 permit the dogs on the conveyor
rollers extending transversely through each of
chains to prolect through the floor and engage
the other recesses, separate supporting means for
the work-piece. These slots’permit the escape
ofv large amounts of heat from the furnace which 45A each recess carried _on-‘said rollers extending
above said furnace floor for supporting work
lowers its efficiency and at the same time cause
special` alloy steel to withstand the temperature,
cold spots in the work. Our invention, utilizing
pieces and> conveying them through said fui'
completely insulated recesses in the furnace floor,
prevents the escape of large quantities of heat
nace,` and- means for operating said rollers‘in
synchronism.
heated uniformly.
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When our invention is applied to a chain con-veyor furnace, it is n'ot necessary for the rollers
to be independentlydriven from an external
REFERENCES YCITED
'The following references' are'of record in the 'ï'
source, as shown on the accompanying drawing
and described above for the roller hearth ar
rangement.
file of this patent:
,
UNITED STATES PATENTS
In this modification, the conveyor
Number
chain or chains are driven by >a suitable external
means, such as an electric motor, and the rollers
are used` merely to support the chains.
It is generally knownthat high temperature
electric furnaces are, very often equipped _with l
_
JAMES L. McFARLAND.
NORMAN B. JONES.
from the furnace and causes the work to be 50
489,017
o
Name
l
Date
Koch _________ __'____ Jan. 3, 1893
786,565
Hughes ___________ -_ Apr. 4, 1905
1,362,369
Talley '_ ___________ _,Dec. 14, 1920
1,825,107
Wean ___________ .__ Sept. 29, 1931
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