Note: Descriptions are shown in the official language in which they were submitted.
N24-42 Can.
106'~0()3
SEaLING BODIES FOR HIGH TEMPE~ATIJRE APPLIC~IONS
The increasing use of high temperature furnaces for the heat ~reat-
ment of various metallic articles at controlled temperature and under
controlled furnace atmospheres has led to considerable changes in furnace
design, These types of furnaces are generally designed for intermittent
operation, with fluctuating heating cycles and periodic removal and
replacement of workpieces. In many applications, the workpiece must be
heated in a controlled atmosphere. This at sphere may be a reducing
gas~ such as carbon monoxide or non-oxidizing, such as nitrogen or argon.
Since the furnace must be readily opened and closed to permit changing
the workpieces, it is apparent that a reliable type of sealing means must
be used around the doors or similar parts of the furnace which are opened
and closed periodically. Adequate seals not onlypermit the retention of
the desired interior atmosphere of the furnace, but they also aid in
maintaining a more even heat distribution to the treated articles within
the furnace.
For furnace operations of this type, satisfactory seals have been
difficult to achieve, due primarily to the high temperatures at which
the seal must function. These temperatures may be as high as 1500-2000F
so that common elastic sealing materials such as rubber, or rubber
coated textile materials are, of course, out of the question. A commonly
used seal is a horizontal channel fllled with sand, into which the
edges of the movable furnace cover can be immersed. While this type
of seal is inexpensive and withstands high temperatures, it can perform
only on a horizontal surface and the sand is easily blown out. Other
types of seals have been developed in which fibers such as those of
asbestos are used. While these may be used on vertical surfaces, the
fibers are rather soft and tend to work loose over a period of time,
thus requiring frequent maintenance to continue their sealing effective-
ness. There is a need, therefore, for an improved resilient type
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of sealing body which can withstand high temperatures and can function
in any position either horizontal or vertical. The sealing body should
be of a type easily installed to replace present sand seals and should
continue its sealing properties with a minimum amount of maintenance.
The invention provides a resilient sealing body for high tempera-
ture applications, the body having flexible longitudinal shape and
comprising fibers of heat resistant material. The body is reinforced
by a flexible heat resistant holding means for retaining the body under
compression. The heat resistant fibers are made from materials such as
aluminum gilicate, alumina, silica, boron carbide, silicon carbide, glass
or mixtures thereof and the holding means may be one or more wires or
S~e/ :
B strips of heat resistant metals such as ~b~ brass, bronze, or stain-
less steel. The sealing body preferably deines a rectangular cross
section and may conveniently be from 9 to 12 inches in length, the
holding means being applied and fastened to hold the body under longitu-
dinal compression.
Fig. 1 shows the resilient sealing body of the invention as a
solid body of fibrous material.
Fig. 2 shows one of the wire loops which is passed through the
resilient sealing body to reinforce it and hold it under compression.
Fig. 3 shows one of the component pieces for a built-up resilient
sealing body of the invention.
Fig. 4 shows the body of the invention as assembled from component
pieces.
Fig. 5 shows a sectional side view of one form of heat treating
furnace, using the resilient sealing body of the invention
Fig 6 shows a sectional top view of the furnace of Fig. 5, shwing
the circular arrangement of the sealing bodies in the furnace base
Fig. 7 shows an enlarged sectional view of the sealing body of the
invention in place within a holding slot in a furnace structure.
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The resilient sealing body of the invention is made from a com-
pressed heat-resistant flexible fibrous material, the body being formed
into a longitudinal or linear shape and being reinforced by flexible
heat resistant holding means, the holding means retaining the body
under longitudinal compression. One form of this body is shown generally
as 12 in Pig. 1, the body being formed from resilient fibrous material
having a felt-like structure, which may be needled if desired. The
body 12 comprises heat resistant fibrous material which is selected
from materials such as alumlnum silicate, alumina, silica, boron car-
bide, silicon carbide, glass or mixtures of these. Aluminum silicate
is a preferred material, fibers of this being available under the
trade mark FIBERFRAN~, a product of The Carborundum Company, Niagara
Falls, N.Y. The body 12 is preferably formed with a rectangular cross
section, as shown in Fig. 1. While this shape is preferred, the body
may be made with a square or circular cross section if desired. The
height and width of the cross sectional dimensions of the body may be
varied as desired to give bodies which will fit snugly within appropri-
ate holding grooves or slots in the surfaces of high temperature appa-
ratus.
The length or linear dimension of the body 12 may vary from about
12 to about 15 inches, the body is then longitudinally compressed to
a length of about 8 1/2 to about 13 inches, corresponding to a reduction
in length or linear dimension to about 70 to about 85% of the uncom-
pressed length of the body. While an 8 1/2 to 13 inch linear dimension
is preferred from the stand point of easier construction and installa-
tion as sealing units, the bodies may be made longer or shorter if
desired for special uses. The body is held under compression by hold-
ing means which may comprise one or more wire loops 14 which are passed
completely through the body from one end, the ends of the loops being
twisted together at the other end to hold the body 12 under compression.
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The loops 14 are shown inserted in the body 12 in Fig. l, one of the
loops is shown separately in Fig. 2. The wire is preferably a stainless
steel o about No. 10 Browne & Sharp gauge (0.102 inches diameter),
although the diameter used may vary from 9 to 11 Brown & Sharpe gauge,
depending upon the density of the fibrous material used in the body. -
While the wire as shown in Figs. 1 and 2 is a preferred holding means,
the invention is not restricted to wire but may employ flexible metal
strips instead. In addition to stainless steel, the wires or strips may
be made of other heat resistant metals such as steel, brass or bronze, ~ --
depending on the type of service in which the sealing body will be used.
Although the sealing body of the invention has been described as a
solid body and illustrated as such in Fig. 1, a preferred embodiment is
a sealing body made from the assembly of a plurality o flat pieces of
1exlble ibrous material. One o these pieces is shown in Fig. 3, the
piece 16 being formed from resilient fibrous material having a felt-like
structure, which may be needled if desired. While a non-woven material
is preferred, the piece 16 may also be made from a woven material. The
fibrous material comprising the piece 16 is heat resistant, the fibers
being selected from materials such as those previously described. The
piece 16 is preferably cut in a rectangular shape, as shown in Fig. 3.
While this shape is preferred, the invention is not restricted to this
but the piece 16 may be square or even circular in shape if desired.
The thickness of the piece 16 is not critical, but may preferably range
from about 1/4 to about 1/2 inch. The height and width of the piece may be
varied as desired, depending on the size required for the finished
sealing body.
The preferred resilient sealing body 18 of the invention is formed
by assembling a plurality of the pieces 16, describing in the preceding
paragraph, in a stacked array, as shown in Fig. 4. Sufficient pieces
are used to form a body with a linear dimension of about 12 to about
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15 inches. This body is then compressed longitudinally to a linear
dimension of about 8 1/2 to about 13 inches, corresponding to a reduction
in length of about 70 to about 85% of the uncompressed length of the
body. The compressed body 18 is held under compression by holding
means such as wire loops 14 which are passed completely through the
stacked array from one end, the ends of the loops being twisted together
at the other end to hold the body 18 under longitudinal compression as
previously described for the solid body 12.
One of the applications in which the sealing body of the invention
is highly effective is shown in Fig. 5, which illustrates a sectional
side view of a heat treating furnace, shown generally at 20. The fur-
nace comprises a metal base plate 22 holding a stool plate 24, the stool
being either metal or ceramic material. The stool 24 supports one or
re workpieces 26 or heat treatment. A circular inner cover 28 encloses
the workpieces and allows the maintenance of a controlled atmosphere 30
around the workpieces during heat treatment. An outer cover 31 (shown
partially) acts to enclose the furnace and heating units (heating units
are not shown). The lower rim of the movable cover 28 rests upon a ring
of sealing bodies 18, the sealing bodies being held in a circular groove
or rectangular cross section 32 which is cut in the base plate 22. In
Fig. 6, a sectional top view above the furnace base plate 22 shows how
the sealing bodies 18 are butted together within the circular groove 32
to give a complete ring of sealing material, shown generally at 34. A
re detailed view of the placement of the sealing body 18 of the inven-
tion is illustrated in Fig. 7. Since the sealing bodies are flexible
and resilient, they can be shaped to be slightly larger than the dimen-
sions of the slot 32, thus insuring a snug fit when inserted in the
slot. The flexibility of the bodies 18 allow them to bend to follow
the curvature of the slot 32. In the installation as shown in Figs.
and 6, the bodies 18 are abutted end to end to give a firm ring 34
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of essentially continuous sealing surfaceO Since the sealing bodies 18
are resilient, the weight of the cover 28 causes its lower rim to depress
the bodiesslightly at the point of contact, thus insuring a satisfactory
seal all around the rim of the coverO The seal thus forméd is markedly
5an.~ :
superior to that formed by the layers of ~R previously used. As
previously noted, sand forms a loose seal and tends to blow out under
momentary gas pressure surges, the sand requiring periodic replacement
to maintain its sealing effectiveness. ~ -
While the resilient sealing bodies of the invention are shown as
replacing horizontal sand seals in a heat treatment furnace, this is
for illustration only and does not limit the seals to thi~ type of
appllcation. It is apparent that the resilient sealing bodies of the
invention may be used equally well in applications requiring vertical
and overhead seals, applications which are impractical for sand seals.
The sealing bodies of the invention may therefore be used for furnace
door seals, soaking pit cover seals and in applications where the seal-
ing gurfaces may be tilted from the horizontal or subjected to mechanical
vibrations. The sectional construction and flexibility of the sealing
bodies permits their rapid installation without the requirements of
refractory cements to hold the sealing bodies in placeO
Repair and replacement of damaged sections is easily made and the
amount of fiber compression in the bodies may be regulated as desired
to give the optimum degree of sealing action best suited to the particular
application desired.
