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Патент USA US3057336

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Oct. 9, 1962
3,057,325
T. E. NANCE
CARBON DEPOSITION APPARATUS
Filed April l, 1959
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INVENTOR
ZkølâfÃ/?žw?
BY
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ATTORNEY
(ice
3,057,325
Patented Oct. 9, 1962
2
chambers exposing the articles to the carbonaceous gas
3,057,325
CARBON DEPOSITION APPARAT US
Taylor E. Nance, Winston-Salam, N.C., assignor to West
em Electric Company, Incorporated, New York, N.Y.,
a corporation of New York
Filed Apr. 1, 1959, Ser. No. 803,529
10 Claims. (Cl. 118--47)
in the deposition chamber only.
More speci?cally carbon deposition apparatus for car
bon coating articles such as ceramic cores includes a pre
heating chamber, a coating chamber, and a cooling cham
ber. Electrical heating elements maintain the deposition
chamber at the correct temperature so as to pyrolize or
crack 'a carbonaceous gas forced through the chamber
causing the carbon in the gas to be deposited on articles
This invention relates to a deposition apparatus and
more particularly to an apparatus for depositing a uni 10 which are rolled through the apparatus between spaced
guide rolls.
form coating of carbon on ceramic cores while rolling
The articles are conveyed through the preheating cham
the cores through a deposition chamber.
ber in an entrance tube which surrounds the guide rolls
and opens into the deposition chamber. An outer tube
carbon on a refract-ory body such as a ceramic core by 15 spaced from and concentric With the entrance tube forms
a closed passage around the entrance tube. Radially
heating the core to a predetermined temperature and
It is the purpose of the invention to form such articles
as deposited carbon resistors by depositing a coating of
then exposing the preheated core while in a rolling condi
spaced ports in the end of the entrance tube adjacent the
deposition chamber open into the closed passage sur
tion to an atmotsphere of carbonaceous gas in a coating
rounding the entrance tube permittíng a neutral or inert
chamber so that the gas is cracked and the carbon con
tained in the gas is deposited on the surface of the ceramic 20 gas to ?ow from a suitable source through the entrance
core. The carbon coating produces highly desirable re
sistance characteristics.
By accurately controllíng the
tube and into the surrounding passage. An exhaust pump
maintains su?icient pressure in the passage to exhaust
the neutral gas from the entrance tube whereby the coat
ing gas is excluded from the entrance tube. The spaced
deposition process, and :thus the amount of carbon de~
posited, a deposited carbon resistor within extremely close
resistance tolerances may be formed. By maintaining a 25 guide rollers roll the coated articles from the deposition
'chamber through a cooling chamber within an exit tube.
?ow of ceramic cores through the carbon deposition
An atmosphere of neutral gas excludes the coating gas
chamber, great quantities of precision resistors or other
from the exit tube while an exhaust pump removes the
articles can be continuously produced.
coating gas and the neutral gas from the deposition
The density and thickness of the carbon coating formed
on the ceramic cores is dependent on the length of time 30 chamber.
A clear Understanding of the invention will be had
the core is exposed to the coating gas, the concentration
from the following detailed description of a speci?c em
of hydrocarbon in the coating gas, and the temperature
bodiment thereof, When read in conjunction with the
to which the core is heated. These factors are critical
and care is necessary to secure a uniform coating of hard
carbon on the ceramic core without forming soot or soft
appended drawings, in which:
carbon deposits.
apparatus;
FIG. 1 is a cross-sectional View of a carbon deposition
FIG. 2 is a partial plan view of a carbon deposition ap
paratus; and
FIG. 3 is a cross-sectional view taken along line 3-3
stream of ceramic cores while at the same time consistent
~ly 'obtaining predetermined results at a satisfactory pro 40 of FIG. 1.
Referring to the drawings a furnace tube 11, composed
duction rate. These attempts have failed because of the
of a refractory material and having headers 12 and 13 of
di?iculty in conveying a continuous stream of ceramic
fused silica, extends through an electric furnace 14. The
cores through a carbon deposition chamber while at the
_furnace 14 is heated by electrical elements 15 spaced
same time precisely controlling the length of time that
the ceramic cores are exposed to the coating gas. This 45 around and along the furnace tube 11. The elements 15
Numerous attempts have been made to devise a carbon
deposition apparatus capable of coating a continuous
is caused by reason of the fact that no e?ective manner
are connected in parallel and are energized from a suit
of scaling the entrance and exit passages through which
the articles must pass into and 'out of the deposition cham
able voltage source 16. A central portion 17 of elements
15 extend through a heating chamber 18, which is formed
of ?re brick or other heat insulating material. The heat
ing chamber 18 surrounds the furnace tube 11 and de?nes
ber has been devised so as to prevent the articles from
being exposed to the coating gas prior to their being re
ceived in the deposition chamber or during their departure
therefrom.
Another inherent dil?culty in present day techniques
of coating articles as they pass through a deposition cham
ber is that of rotatively supporting an article While at the
a central hot zone within the furnace 14.
A cylindrical
furnace líner 19 of a highly heat conductive material such
ras silicon carbide is secured within the furnace tube 11
and de?nes a deposition chamber 21.
An entrance tube 22 secured .to the inner face of the
header 12 extends through and de?nes a preheating cham
same time exposing the entire surface area of the article
ber 23 within a portion of the furnace tube 11. The en
to the coating gas.
trance tube 22 and the preheating chamber de?ned there
An object of this invention is to provide an apparatus
by open into the deposition chamber 21. An outer tube
for depositing a uniform coating of carbon on articles.
Another object of this invention is to provide an ap 60 24 mounted concentric with the entrance tube 22 and
spaced from the furnace tube 11 is rigidly secured to an
paratus for depositing a uniform coating of hard carbon
inner side wall face of the header 12. An end cap 25
on ceramic cores as they are continuously rolled through
secured to the end of the outer tube 24 and the entrance
the coating apparatus.
tube 22 adjacent the deposition chamber 21 forms a
To accomplish these and other objects carbon deposi
closed passage 26 between the entrance tube 22 and the
tion apparatus embodying certain features of this inven
outer tube. Radially spaced ports 27 formed in the end
tion may include a preheating chamber, a deposition
of the entrance tube 22 open into the closed passage 26.
chamber, and a cooling chamber. A conveyor rolls
An exit tube 28 secured to .the inner face of the header
ceramic cores through the deposition chamber at a uni
13 extends through and de?nes a cooling chamber 29
form rate of speed where a carbonaceous gas is cracked or
pyrolized and a uniform coating of carbon is deposited 70 within a portion of furnace tube 11. The exit tube 28“ and
the cooling chamber 29 de?ned thereby opens into the
on the ceramic cores. A gaseous atmosphere excludes
deposition chamber 21.
`the carbonaceous gas from the preheating and cooling
3,o57,325
A suitable source of carbonaceous coating gas 31 such
as methane and intermixed with a suitable carrier gas such
as nitrogen is connected through a tube 32 into a passage
33 surrounding the outer tube 24 which opens into the
deposition chamber 21. An exhaust pump 34 is connected
with a passage 35 surrounding the exit tube 28 and which
opens into the deposition chamber 21. The exhaust pump
4
spiral grooves 43, the ceramic cores 37 Will be simultane
ously rotated and conveyed through the furnace 14 where
they are uniformly coated with carbon. The speed of
rotation and horizontal movement of the ceramic cores
may be varied by adjusting the speed of the motor 49 and
varying the pitch of the spiral grooves 43. The ceramic
cores 37 are supported by and rotate upon the edges 44
of the base pans 41 and 42.
34 draws the coating gas through the passage 33, the
The ceramic cores 37 pass through the furnace 14
deposition chamber 21, and out through the passage 35
into the atmosphere or a suitable gas collector. The coat 10 between the guide rolls 38 and 39' into a receiving cham
ber 55 Secured to the header 13. An end portion 56 of
ing gas is diffused throughout the deposition chamber 21.
each of the guide rolls 38' and 39 is reduced in diameter to
The type of coating gas which may be used is not re
the depth of the spiral grooves 43 and is supported in a
stricted to methane or other gases in the methane series.
suitably mounted bearing '57. A hopper 58, supported
As is well known, many other types of gas rich in hydro
carbon may be employed. By the proper choice of coat 15 directly below the reduced end portions 56 and extending
through the receiving chamber `55 receives the carbon
ing gas, and additives mixed therewith if desired, and of
coated cores 37 as they roll out of the spiral grooves 43
the temperature within the deposition chamber, the carbon
in the gas will be deposited as a hard ?lm on articles ex
posed to the coating gas within the deposition chamber
21. By controlling the duration and manner of exposure
of the article to the coating gas a uniform ?lm of hard
carbon will be deposited on the article. This ?lm when
deposited on ceramic cores or other refractory bodies
gives the core a very desirable resistance characteristic.
In the manufacture of deposited carbon resistors it is 25
mandatory that the physical characteristics of the carbon
formed in the guide rolls 38 and 39. The cores 37' are
supported within the hopper 58 on one or the other of
a pair of alternately reciprocable slides 59 which are
actuated by pneumatic or other means (not shown). As
the slides 59` are reciprocated the cores 37 pass from the
hopper 58 into a discharge tube 61 which transports the
cores to a next desired position.
A neutral gas such a nitrogen, supplied under pressure
from a pump 62. in a tube 63, passes into the feeding
chamber 541 and through the aperture 40 into the entrance
tube 22. The nitrogen gas provides a protective atmos
coating formed on ceramic cores be precisely controlled
in order to produce the desired resistance value within
phere within the feeding chamber '51, preventing the
close tolerances.
A conveyor assembly 36 for transporting a series of 30 cores 37 from being contaminated before entering the
furnace 14. An exhaust pump 64', connected to the
ceramic cores 37 or other refract'ory bodies through the
passage 26 through a tube 65, draws the neutral gas
furnace 14 comprises a pair of spaced parallel guide rolls
through the feeding chamber 51, the entrance tube 22, the
38 and 39 rota?tively supported at both ends and within
radial-ly spaced ports 27, and through the passage 26 into
base pans 41 and 42. The guide rolls 38 and 39* and
the atmosphere. By maintaíning a negative pressure in
their respective base pans 41 and 42 pass through aper
the passage 26 by means of the pump 64 the neutral gas
tures 40 in the headers 12 and 13, the entrance tube 22, the
is withdrawn with su?icient velocity so as to prevent the
deposition chamber 21, and the exit tube 28, respectively.
neutral gas from entering the deposition chamber 21 or
As shown in FIG. 2, a spiral groove 43 of rectangular
the coating gas from contacting the ceramic cores 37 until
cross section is formed in each of the guide rolls 38 and
39 and extends along their length. The grooves 43 are 40 they enter the deposition chamber 21. As the cerarnic
cores 37 are transported through the entrance tube 22
identical in pitch, one groove forming a left-hand thread
they are preheated to the desired temperature by the
in guide roll 38 and the other forming a right-hand thread
elements 15 surrounding the furnace tube 11.
in the guide roll 39.
A neutral gas such as nitrogen supplied under pressure
The ceramic cores 37 are supported between and
perpendicular to the spaced guide rolls 38 and 39` on an 45 from a pump 66 in a tube 67 passes into the receiving
chamber 55 and through the aperture 40 into the exit
upturned edge 44 formed on each of the base pans 41 and
tube 28. The nitrogen gas ?ows through and is swept
42 while the ends of the ceramic cores 37 are received in
out of the end of the exit tube 23 adjacent the deposition
the spiral grooves 43. 'Ihe core 37 is preferably sup
chamber 21 where it turns sharply and is exhausted by
ponted such that its horizontal axis will lie in a plane ex
tending between the horizontal aXes of the guide rolls 50 the pump 34 along with the coating gas and other prod
ucts of the cracking process. The nitrogen gas excludes
38 and 39.
the coating gas from the exit tube 28 and provides a pro
Intermeshing gears 45 are Secured t'o a reduced end
tective atmosphere in which the coated ceramic cores 37
portion 46 -on each of the guide rolls 38 and 39. A
are cooled before they are removed from the furnace 14.
drive gear 47, ?xed to a shaft 48 which is driven by a
motor 49, meshes with one of the gears 45 to rotate the 55
operation
gears 45 and the guide rolls 38 and 39 in opposite
Ceramic cores 37 are fed in seriation from the supply
directions. The guide rolls 38 and 39` may be driven by
hopper 52 within the protective atmosphere of the feed
separate motors if desired. The shaft 48 passes through
ing chamber 51 to the guide rolls 38 and 39 where they
a seal in the wall of a feeding chamber `51 formed
around the end of the guide rolls 38 and 39 and Secured to 60 are received in the spiral grooves 43. As the guide rolls
38 and 39 are counter-rotated, the cores 37 -will be rotated
the header 12.
along the edges 44 of the base pans 41 and 42 into the
A hopper 52 mounted above the guide rolls 38 and
furnace 14. As the cores pass through the inert gaseous
39 and extending through the feeding chamber 51 sup
atmosphere maintained within the entrance tube 22, they
ports a vertical column of horizontally disposed ceramic
cores 37 directly over the spaced guide rolls 38 and 39. 65 are preheated to the desired temperature by the heating
elements 15. The preheated cores 37 continue to rotate
The ceramic cores 37 are fed into the hopper 52 through
along the edges 44 of the base pans 41 and 42 into the
a supply tube 53. The cores 37 are supported within the
deposition chamber 21 where they are exposed to a
hopper 52 on slides 54 which are alternately reciprocated
carbonaceous coating gas of methane supplied from the
by pneumatic or other suitable means (not shown) to feed
the ceramic cores 37 one at a time to the guide rolls 38 70 tank 31. The inert gas supplied by the pump 62 is
drawn through the feeding chamber 51, the entrance tube
and 39. As the cores 37 fall from the hopper 52, they
22, and the radial ports 27 into the passage 26 by the
are supported on the edge 44 of the base pans 41 and 42,
pump 64 with sui?cient velocity and pressure to seal the
and the ends of the cores are received within the spiral
preheating chamber 23 -from the deposition chamber 21
grooves 43. Due to the counter-rotation of the guide
rolls 38 and 39 and the opposite threads formed by the 75 and exclude the coating gas from the entrance tube 22.
&0573325
5
6
This action shields the ceramic cores 37 from the coat
ber, spaced rotatable members for receiving the ends of
ing gas until they enter the deposition chamber 21.
the ceramic cores and for rolling the ceramic cores in
a direction normal to their longitudinal axes through the
As the ceramic cores 37 pass into the deposition cham
ber 21 they are heated to a desired ?nal temperature.
When the coating gas Contacts the heated cores 37, it is
cracked and the carbon in the gas is deposited on the
deposition chamber, an entrance tube through which
articles to be coated are conveyed into the deposition
chamber, means for heating the deposition chamber to
crack the coating gas in the deposition chamber, an exit
grooves 43 and the edges 44 of the base pans 41 and
tube in which the articles are conveyed from the deposi
42, the ceramic cores 37 are supported between the guide
tion chamber, a tube mounted concentrically with and
rolls 38 and 39, and are continuously rotated within the 10 surrounding the entrance tube, a cap on the end of the
deposition chamber 21. The surface area of each of the
concentric tubes adjacent the 'deposition chamber form
ce?'amic cores is evenly exposed to the coating gas as
ing a closed passage between the entrance tube and the
suring uniform coating. The speed of rotation of the
concentric tube mounted therewith, notches formed in
ceramic cores 37 may be precisely regulated by adjusting
the end of the entrance tube and opening into said pas
the speed of the motor 49 or changing the pitch of the 15 sage, and means for maintaining an inert gaseous atmos
spiral grooves 43. The rate of travel of the cores
phere in the entrance and exit tubes whereby the arti
through the furnace is controlled by adjusting the speed
cles to be coated are exposed to the coating gas only
of motor 49. The conveyor assembly 36 can be readily
in the deposition chamber as they are conveyed through
adjusted to transport diñerent lengths of articles by vary
the furnace.
ceramic cores 37 as a hard ?lm.
Because of the spiral
ing the spacing of the guide rolls 38 and 39 and adjusting 20
4. Apparatus for conveying cylindrical articles com
the drive mechanism therefor.
prising a pair of spaced parallel guide rolls having oppo
As the coated cores 37 leave the deposition chamber 21
site threads formed along their length, means for sup
they enter a protective atmosphere of nitrogen or other
porting the articles between the guide rolls and within
inert gas within the exit tube 28. The nitrogen gas is
the opposite threads formed therein, and means for
counter-rotating the guide rolls whereby the articles are
supplied under pressure from a suitable source by the
rotated within the opposite threads and along the length
pump 66 and ?ows in a direction opposite to that of
of the guide rolls.
the ceramic cores 37. As the nitrogen gas passes out of
5. Apparatus for rolling cylindrical bodíes comprísíng
the exit tube 28 it is turned sharply, and is withdrawn
a pair of spaced guide rolls having opposite threads
along with› the coating gas and other products of the
cracking process through the passage 35 by the pump 34. 30 formed along their lengths, means for placing the cylin
drical bodíes between the guide rolls, means for support
This action excludes the coating gas and other products
ing the cylindrical bodíes between the guide rolls and
of the cracking process from the exit tube 28 and pro
within the opposite threads formed therein, and means
vides a protectíve atmosphere for the coated cores 37.
for rotating the guide rolls in opposite directions whereby
The coated cores 37 are cooled as they pass through the
the cylindrical bodíes are rotated within the opposite
exit tube 28 before entering the receiving chamber 55.
threads and rolled along the length of the guide rolls.
The uniformly coated cores 37 remain within the spiral
6. A carbon deposition furnace for coating cerarnic
grooves 43 until they reach the reduced end portion 56
cores which comprises a preheating chamber, a deposi
of the guide rolls 38 and 39 where they roll out of the
tion chamber, and a cooling chamber, spaced rotatable
grooves 43 into the hopper 58 where they are fed into
members for conveying ceramíc cores to be coated
the discharge tube 61 by the alternately reciprocating
through the preheating, deposition, and cooling chambers,
slides 59.
means for conducting a carbonaceous gas through said
It is to be understood that the above described appara
deposition chamber, means for heating the deposition
tus is simply illustrative of the application of the broad
chamber to crack the carbonaceous gas, an entrance tube
principles of the invention. Numerous other arrange
through which the ceramic cores to be coated are con
ments may be ?devised by those skilled in the art which
veyed through the preheating chamber and into the
will embody the principles of the invention and fall
deposition chamber, an outer tube spaced from and con
within the scope thereof.
centric with the entrance tube and forming a closed pas
What is claimed is:
sage about said entrance tube, radial ports formed in the
1. Deposition apparatus for coating ceramic cores
which comprises a preheating chamber, a deposition 50 end of the entrance tube adjacent the deposition chamber
and opening into said closed passage, a source of neutral
chamber, a cooling chamber, conveyor means for support
gas connected to the entrance tube, a pump for withdraw
ing only the ends of the ceramic cores and for rolling
ing the neutral gas from the entrance tube through the
the ceramic cores through said preheating, deposition, and
radial ports and out the closed passage whereby the coat
cooling chambers, means for conducting a carbonaceous
ing gas is excluded from said entrance tube, an exit tube
coating gas through said deposition chamber, means for
in which the cores are conveyed from the deposition
heating the deposition chamber to crack the gas and de
chamber and through the cooling chamber, a source of
posit a coating on the ceramic cores, and means «for ex
neutral gas connected to the exit tube, and a pump for
cluding the coating gas from the preheating and cooling
withdrawing the neutral gas from the exit tube in a direc
chambers.
2. A carbon deposition furnace for coating ceramíc 60 tion which is opposite to the direction of travel of the
ceramic cores and for withdrawing the neutral gas and
cores comprising a deposition chamber, means for main
the coating gas from the furnace whereby the coating gas
taining a continuous ?ow of a carbonaceous coating gas
is excluded from the exit tube.
throughout said chamber, conveyor means for rolling the
7. In a conveying apparatus, a pair of spaced supports,
ceramic cores through the deposition chamber, an en
trance tube through which articles to be coated are con 65 a pair of threaded members mounted for rotation above
the outer edges of the respective supports, means for feed
veyed into the deposition chamber, an exit tube in which
ing articles between said members so that the ends project
the articles are conveyed from the deposition chamber,
into the threaded members, and means for rotating said
and means for maintaining an inert gaseous atmosphere
members to advance the articles along the supports.
in the entrance and exit tubes whereby the articles to be
coated are exposed to the coating gas only in the deposi 70 8. In an article advancing apparatus, an elongated sup
tion chamber.
port, a pair of members having threaded sections, means
3. A carbon deposition furnace for coating ceramic
for mounting said members for rotation above opposite
edges of one surface of said support, means for feeding
ing a carbonaceous coating gas through said chamber,
articles onto said support so that the ends project into
means for exhausting the coating gas from said cham 75 the threaded sections, and means for rotating said threaded
cores comprising a deposition chamber, means for pass
3,o57,325
7
members to advance and roll said articles along said sup
port.
9. In a coating apparatus, an entry chamber, a coating
chamber at the terminus of and opening into said entry
chamber, van exit chamber at the terminus of and opening
into said coating chamber, means for supplying neutral
gas to said entry chamber, means for exhausting said neu
tral gas from said terminus of said entry chamber, means
for supplying a coating gas to said coating chamber,
means for supplying neutral gas to said exit chamber, 10
means for simultaneously exhausting said coating gas and
said neutral gas at the entrance of said exit chamber, and
means for rolling cylinclrieal articles through said entry,
coating, and exit chambers.
10. Apparatus for transporting cylindrical bodies which 15
comprises a pair of spaced Parallel guide rolls having
identical but opposite threads formed along their lengths,
a pair of spaced parallel base pans, each having an up
turned edge secured beneath the guide rolls and extending
along its length for supporting the cylindrical bodies be 20
8
tween the guide rolls and within the opposite threads
formed therein, and means for counter-rotating the guide
rolls Whereby the cylindrical bodies supported between
the guide rolls -are rotated within the opposite threads in
the guide rolls and rolled along the upturned edges of the
base pans.
References !cited in the ?le of this patent
UNITED STATES PATENTS
l,564,926
2,328,422
Armstrong et al _________ __ Dec. S, 1925
Christensen ________ __,__ Aug. 31, 1943
2,778,743
2,810,365
Bowman _____________ __ Jan. 22, 1957
Keser ________________ __ Oct. 22, 1957
612,742
800,841
Great Britain _________ __ Nov. 17, 1948
Germany _____________ __ Dec. 11, 1950
146,834
Australia _____________ _._ June 13, 1952
882,074
Germany ______________ __ July 6, 1953
FOREIGN PATENTS
L.ac .
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