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Патент USA US3081999

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March 19, 1963
Filed Dec. 9, 1959
2 Sheets-Sheet l
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FIG. 2.
6/2 574k? a
26) I
FIG. 1.
United States Patent 0
Patented Mar. 19, 1963
‘Salt for heating the work in the chamber 3 is heated
and kept molten in chamber 1, and is circulated through
Frederic O. Hess, Philadelphia, Pa., assignor to Selas
Corporation of America, Dresher, Pa., a corporation of
the passages 8 and 9‘ between the two chambers so that
the molten salt can heat work in chamber 3. The salt
is heated and kept in its melted condition by means of
a heating unit 12 which includes an inner refractory
Filed Dec. 9, 1959, Ser. No. 858,410
member 13, which has the same shape as the interior
7 Claims. (Cl. 266—4)
of chamber 1, but is smaller in size than that chamber.
In the drawings, this chamber is shown as being cylindri
The present invention relates to furnaces, and more
particularly to furnace-s of the salt bath type- that are 10 cal, but it could take any other desired shape. The re
fra‘ctory member is shorter than the depth of chamber
1, and is provided with a radially extending ?ange 14
In most salt bath furnaces there is the problem of
which rests on the upper edge of the open chamber to
spattering hot salt when work is inserted into and re
close this chamber during the time the heating unit is in
moved from the bath. A further problem is the drain
ing of the hot salt from time to time, from the space in 15 heating position as shown in FIG. 1. A shell 15 of
an alloy steel, that will Withstand the temperatures en
‘which the work is heated, when cleaning is necessary.
countered and which will not be harmed by the salt,
It is an object of the invention to provide a salt bath
surrounds and is spaced from the refractory cylinder.
furnace in which the salt is removed from the work heat~
This shell is supported on ?ange 14 by means of bolts
ing space when work is inserted into and removed there
from. i It is a furtherobject of the invention to provide 2,0 16 which extend through the ?ange. These bolts have
yokes 17 at their lower end, the arms of which extend
a ‘furnace in which salt is heated to an even temperature
on each side of the shell and are provided with openings
and is circulated around the work while it is being heated.
through which a pin -18 extends. The position of the shell
In practicing the invention, there is provided a furnace
with respect to the refractory member 13 can be adjusted
having a salt melting area with a bottom on one level
and a work heating area on a second and higher level. 25 by nuts 19. Normally, the nuts will be adjusted to bring
the shell up against spacers 21 which locate'the shell
These areas are connected by passages through which the
with respect to the refractory member, both axially and
salt can be circulated. ‘The salt is heated by a heating
radially. The distance between the burners, described be
unit that can be raised and lowered in the salt melting
low, and the bottom of shell 15 can be varied to give
area, thereby changing the level of the salt. Thus, when
the heating unit is lowered into the melting area, the 30 as large a combustion space as is necessary or desired.
' The limiting position is to have the bottom of struc
salt level is raised sufficiently for the salt to flow into
ture 13'level with ?ange 14.
the work heatingiarea and cover work placed‘therein.
The heating unit is built around a structural steel
With such an arrangement, work can be placed on and
frame 22, and the entire unit may be raised and lowered
removed from a dry hearth while the salt ‘is continually
35 by cables 23 which are attached to the frame. These
being maintained at the desired temperature.
cables pass over a pulley 24 and are wound upon a
It is obvious thatthe apparatus could be ‘used where
drum 25 that is operated by a reversible motor (not
other material than salt is to be used as the heating
shown). With this arrangement, the heating unit can
medium such as lead or some ‘other metalfor example.
be lowered into heating position shown‘in FIGS. 1 and
The various features of‘ novelty which characterize
my invention are pointed out with particularity in the 40 2 of the drawings, or it can be moved up to a position
claims annexed to and ‘forming a part of this speci?ca- ' inwhich the entire unit is out of chamber 1 to give access
to the salt therein for cleaning or replenishing the salt.
tion. For a better understanding of the invention, how
The heating unit is heated ‘by a plurality of burners ‘26
ever, its advantages. and speci?c objects attained with
which are shown herein as being of the radiant cup type
its use, reference should be had to the accompanying
and as being located at spaced points in the bottom of the
drawings and descriptive matter in which I have illus
refractory member. These burners are connected by ‘a
trated an described a preferred embodiment of the
fuel supply manifold 27 that is in turn supplied by a
?exible pipe 23 extending between the manifold and a
In the drawings:
FIG. 1 is a section through the furnace taken on line 50 gas supply pipe. The pipe 123 is sufficiently ?exible so
used for heat treating or melting of metal.
1—1 ofFIG. 2,
that it can be bent as the heating unit is raised and
lowered. When the burners are ?red, they serve to heat
shell 15, which in turn transfers the heat to the salt.
'FIG. 2 is a section‘ taken on line 2--2 of FIG. 1, '
‘ FIG. 3 is a section through a portion of the furnace
taken on line 3-—-3 of FIG. 1, and
_ FIG. 4 is a-section similar to FIG. 1 showing a modi
The most intense heat is, of course, directly in front of
the burners on the bottom of the shell, but during opera
tion of the apparatus, the hot products of combustion will
?ow through the space 29 between the refractory member
Referring to FIGS. 1 to 3 of the drawing, there is
and the shell, and ‘will heat the entire surface of the shell j
shown a furnace which includes a salt chamber 1 having
to a high temperature. The products of combustion'are
a bottom 2 and a work heating chamber 3‘ having abot
tom 4 upon which there is placed a plate 5 forming a 60 exhausted from space 29 between‘ the upper edge of the
shell‘a'nd ?ange '14. These products of combustion then
hearth to receive the work 6. ‘It willv be noted that the
‘flow through a space 31 across the top of chamber 3 and
?oor .of chamber 1 is considerably below the floor of
?ed form of the work chamber.
chamber 3.
These structures are made of refractory
under a removable cover 32, heating the top of the cham
ber, to be exhausted through a vent 353. Additional
in accordance with ordinary furnace practice and are sup
ported by a structural steel framework. Thegchambers 65 burners can be used in cover 32 over chamber 3 if they
are necessary. Such burners could also be used to ‘pre
1 and 3 are separated by a partition 7, also of vrefractory
heat this chamber.
material, which has a pair of lower passages? in it and
When the furnace is in operation, salt is circulated
aspair of upper passages 9, as shown best in FIG. 3. by
through-the passages S and 9 of the partition‘7 by means,
means, of which. the two chambers are connected. ‘The
upper passages 9 have a curved surface shown -by line 70 of a pair of paddle wheels 34 and 37 which rotate in op
11, which curves downwardly toward chamber 3..for a
purpose to be described.
' posite directions. Paddle wheel 34 is mounted on a shaft
35 and is driven by a motor 36 that is mounted on a suit
able support outside of the furnace chamber. In a like
by them with the salt against de?ector '41 so that they
manner, paddle wheel 37 is mounted on a shaft 38 and
will be forced below the surface of the salt. Since the
driven by a motor 39. It will be noted that the paddle
salt is above the melting temperature of the aluminum,
wheels are at an elevation so that their shafts are above
and since the aluminum is heavier than the salt, the alu
minum will be melted by the salt, and 'will sink below the
the side walls of chamber 3. Suitable slots are provided
in cover 32 for the shafts to extend between the motors
and the paddle wheels. A de?ector 41 extends across the
work chamber to direct the salt flow downwardly along
surface 11 of passage 9, thereby to insure that there is a
good circulation of the salt through work chamber 3.
In the operation of the furnace, the heating unit 12
is raised, and salt of the proper type and amount is placed
in chamber 2. The burners in the unit are ignited, and
the heating unit is gradually lowered. The hot bottom
surface of shell 15 will begin the melting process, and 15
From time to time as additional aluminum is
added to the bath, the heating unit 12 must be gradually
raised in order to keep the level of the salt at 47, as this
salt is displaced in the melting chamber by the addition
of the ‘aluminum.
When the aluminum has reached a
level substantially equal to the bottom of passage 9, it
must be drained from the chamber to make place for the
addition of more aluminum.
An arrangement of this type is of particular advantage
in the melting of aluminum chips, since these chips in
as the salt is melted, the heating unit can be lowered with
dividually will have a tendency to ?oat on the surface of
the molten salt rising in chamber 1 around the shell.
the salt, and thereby become oxidized. The chips in
There is suf?cient salt placed in the chamber so that when
this case, however, are falling on the surface of the salt
the heating unit is raised, the salt will have a lower level
immediately in front of the paddle. They will be forced
indicated by the line 42, which is just below the ?oor 4 of 20 by the paddle against the de?ector and will sink as they
work chamber 3. When the salt is completely melted
are being melted and before they have had time to be
and the heating unit is in its ‘low position shown in FIG. 1
come oxidized. Since the salt always ?oats on top of the
of the drawing, the salt will havereached a level shown at
aluminum, it is only necessary to raise the heating unit
43, which is sufficient to cover the work 6 that has been
suf?ciently for the salt to ?ow out of the melting cham
placed in chamber 3. When the salt has melted and the 25 ber to expose the entire melt of aluminum. The cham
furnace is operating, the paddle wheels rotating in oppo—
ber can then be drained and cleaned as is necessary from
site directions will circulate salt through the work cham
ber and back to the heating chamber. Thus, the work is
immersed in the salt, which is always kept at an optimum
time to time.
With this arrangement, the salt is auto
matically drained from the melting chamber prior to the
time the aluminum is removed to leave an empty cham~
temperature by the circulating system. 'Furthermore, the 30 ber when cleaning is necessary.
exhaust gases from the burners passing over the top of
From the above description, it will be seen that the
salt in chamber 3 are suf?ciently hot to prevent this. salt
salt bath furnace described herein has the advantage of
from chilling. The unit, therefore, keeps a constant salt
melting the salt in one chamber, which can be kept at an
temperature throughout the level of the salt in chamber 3.
optimum temperature, and of heating the work in a sec
Prior to heating a piece of work, cover 32 is lifted off 35 ond chamber. The arrangement is such that the work
the top of chamber 3 by means of a suitable ring 44, and
chamber can be emptied of salt so that the work can be
the heating unit is raised to its elevated position. In so
placed into the chamber and removed therefrom easily
doing, the level of the salt in chamber 3 falls to a point
and quickly, with no chance of hot salt being splashed
below the ?oor of this chamber. The salt is maintained
over the surroundings. Although the apparatus is par
in a heated condition during this time by its engagement 40
ticularly adapted to be used for a salt bath furnace, it is
with the bottom portion of shell 15. The heating cham
obvious it could be used when other materials, such as a
ber is now empty of salt so that the work piece can be
metal, is the heating medium. Such heating material is
placed in chamber 3 and accurately positioned on hearth
to be contemplated in the claims annexed hereto.
5. This can be done in the open without any splashing
While in accordance with the provisions of the statutes,
of the molten salt over the surroundings. The top is 45
illustrated and described the best form of em
then placed over chamber 3, and the heating unit low
bodiment of my invention now known to me, it will be
ered. During this latter operation, the salt level rises
apparent to those skilled in the art that changes may be
from below the floor of chamber 3 -to above the top of the
made in the ‘form of the apparatus disclosed without de
work piece. The salt is then circulated while the piece is
being heated. When the heating is ?nished, the heating 50 parting from the spirit and scope of the invention set
forth in the appended claims, and that in some cases cer
unit can be raised in chamber 1 to lower the level of salt
tain features of my invention may be used to advantage
in chamber 3 so that the work is exposed for easy re
without a corresponding use of other features.
moval. It is noted that deflector 41 will serve to drive
What is claimed is:
the salt downwardly through passages 9 so that a good
1. In a salt bath furnace, structure ‘forming a ?rst
circulation is obtained throughout the entire volume of 55
chamber having a ?oor at one level in which work is to be
the heating chamber.
heated, and a second chamber in which salt is to be melted
In FIG. 4 of the drawing there is shown a form of the
having a ?oor at a lower level, a partition separating said
invention that can be used for melting metal and which is
particularly adapted for the melting of aluminum chips.
chambers, said partition having passages therein at sub
Referring to that FIGURE, it will be seen that the bottom 60 stantially the level of the ?oor ‘of said ?rst chamber
through which salt may ?ow, a heating unit for the salt,
of the work chamber indicated at 45 is sloping and is
and means to move said heating unit into and out of said
provided with an outlet spout 46 through which the
second chamber thereby to displace salt in said second
molten metal can flow. Normally, this spout would be
chamber through said passages to vary the level of the
closed by a suitable stopper so that the metal would only
be removed from time to time. It will also be noted, by 65 salt in said ?rst chamber.
referring to the FIGURE, that the lower passages 8 in
2. The combination of claim 1 in which said heating
partition 7 have been eliminated.
unit includes a burner ‘and including a removable cover
In the operation of this embodiment of the invention,
over said ?rst chamber, and means to direct combustion
the heating unit 12 is moved to the desired lower posi
gases from said burners between said ?rst chamber and
tion, thereby raising the salt level in chamber 3 to a point 70 cover.
indicated by line 47. This salt is circulated as described
3. In a salt bath furnace, structure ‘forming an open
above by means of paddles 34 and 37. Aluminum chips,
for example, are dropped to the work chamber through
a spout 48 formed in top 32. These chips fall into the
salt immediately in front of the paddles, and are moved
top heating chamber for the salt, a heating unit com
prising a shell of heat conducting material of a size to be
received in said chamber and means in said shell including
a plurality of burners to heat said shell by the burners
and combustion gases produced thereby, means to support
passages, whereby ?uid can ?ow through said passages
said heating unit over said chamber for movement into
and out of said chamber to heat the salt therein and to
vary the level of the salt depending upon how far said
heating unit is moved into said chamber, a second champ
ber in which work to be heated is placed, and means
to said chamber to heat work therein, and means to heat
the ?uid in said reservoir.
6. The combination of claim 5 in which said passage
forming means has displaced passages between said cham
ber and reservoir, and means in said passages to circulate
salt between said chamber and reservoir.
lforming passages to connect said chambers, said passages
7. In a salt bath furnace, structure forming a ?rst
opening into said ?rst chamber at a level between the
chamber in which metal is to be melted, a second cham
maximum and minimum levels reached by the salt as said
heating unit is moved into and out of said ?rst chamber. 10 ber in which salt is to be melted, means forming a parti
tion having a passage therein between said chambers,
4. In a furnace, structure forming an open top cham
said passage being above the level of metal in said ?rst
ber in which a material is to be melted, a heating ele
chamber, means to circulate molten salt between said
ment, means to mount said heating element for vertical
chambers through said passage, means through which
movement into and out of said chamber, said heating ele
ment including an outer shell of heat conducting material 15 metal to be melted can be introduced in said ?rst chamber
and below the salt therein, and means to maintain con
having sides and a bottom and an inner member of re
stant the level of the salt in said chambers as the salt is
fractory material of substantially the same shape as said'
displaced by the addition of metal to said ?rst chamber.‘
shell and spaced therefrom, a burner in said inner mem
ber operative to heat directly the bottom ‘of said shell
with the products of combustion from said burner ?owing 20
through the space between said inner member and shell
to heat the sides of said shell, and means to raise and
lower said heating element.
5. In a furnace, structure forming a chamber having a
?oor upon which work to be heated is placed, structure 25
forming a reservoir for a heating ?uid, the bottom‘ of said
reservoir being below said ?oor, means donning pass-ages
between said chamber and said reservoir at substantially
the ‘level of said ?oor, a displacing element, means to
move said element into and out of said reservoir to vary 30
the level of the ?uid therein from below to above said
References Cited in the ?le of this patent
1,513,875 '
Wilke ________________ __ Nov. 4, 1924
Wallerius ____________ _- July 18, 1950
Gilliland ____________ _.. Oct. 17, 1950
Ankersen ____________ __ Dec. 17, 1957
Adams _______________ __ Sept. 9, 1958
Great Britain __________ __ Apr. 6, 1938
Great Britain _________ __ Ian. 27, 1954
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