Coating apparatus – Gas or vapor deposition
Reexamination Certificate
2001-06-05
2004-07-06
Lund, Jeffrie R. (Department: 1763)
Coating apparatus
Gas or vapor deposition
C118S724000, C118S725000, C118S728000
Reexamination Certificate
active
06758909
ABSTRACT:
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
The present invention is generally directed to Chemical Vapor Deposition/Infiltration (CVD/CVI) apparatus and processes, and more particularly to a method and apparatus utilizing a flow direction nozzle in a CVD/CVI furnace for improving CVD/CVI process time and reducing gas leakage.
BACKGROUND OF THE INVENTION
Chemical vapor deposition and infiltration (CVD/CVI) is a well-known process for depositing a binding matrix within a porous structure. The term “chemical vapor deposition” (CVD) generally implies deposition of a surface coating, but the term is also used to refer to infiltration and deposition of a matrix within a porous structure. The term CVD/CVI is intended to refer to infiltration and deposition of a matrix within a porous structure.
CVD/CVI is particularly suitable for fabricating high temperature structural composites by depositing a carbonaceous or ceramic matrix within a carbonaceous or ceramic porous structure resulting in very useful structures such as carbon/carbon aircraft brake disks, and ceramic combustor or turbine components. The generally known CVD/CVI processes may be classified into four general categories: isothermal, thermal gradient, pressure gradient, and pulsed flow. The specific process times and steps, reactant gas and CVD/CVI furnaces and associated apparatus may vary depending on which of these four general categories is utilized.
U.S. Pat. No. 6,162,298 and corresponding European Patent Application EP 0 997 553 A1 to Rudolph describe these and other CVD/CVI processes and apparatus in further detail. Rudolph particularly describes a sealed reactant gas inlet for a CVD/CVI furnace.
FIG. 1
is a side cross-sectional view of a furnace according to U.S. Pat. No. 6,162,298. A generally cylindrical furnace
10
configured to be employed with a high temperature process is shown. The furnace includes a steel shell
12
and a steel lid
14
. The shell
12
includes a flange
16
and the lid
14
includes a mating flange
18
that seals against flange
16
when the lid
14
is installed upon the shell
12
, as shown in FIG.
1
. The lid also includes a vacuum port
20
.
The shell
12
and lid
14
together define a furnace volume
22
that is reduced to vacuum pressure by a steam vacuum generator (not shown) in fluid communication with the vacuum port
20
. The shell
12
rests upon a multitude of legs
62
. The furnace
10
also includes a cylindrical induction coil
24
adjacent a cylindrical susceptor
26
. The induction coil
24
includes coiled conductors
23
encapsulated by electrical insulation
27
.
During operation, the induction coil
24
develops an electromagnetic field that couples with the susceptor
26
and generates heat within the susceptor
26
. The induction coil
24
may be cooled, typically by integral water passages
25
within the coil
24
. The susceptor
26
rests upon a susceptor floor
28
and is covered by a susceptor lid
30
. A cylindrical insulation wall
32
is disposed in between the susceptor
26
and the induction coil
24
. A lid insulation layer
34
and a floor insulation layer
36
are disposed over the susceptor lid
30
and beneath the susceptor floor
28
, respectively.
The susceptor floor
28
rests upon the insulation layer
36
, which, in turn, rests upon a furnace floor
38
. The furnace floor
38
is attached to the shell
12
by a floor support structure
40
that includes a multitude of vertical web structures
42
.
A reactant gas is supplied to the furnace
10
by a main gas supply line
44
. A plurality of individual gas supply lines
46
are connected in fluid communication with a plurality of gas ports
48
that pass through the furnace shell
12
. A plurality of flexible gas supply lines
50
are connected in fluid communication with the gas ports
48
and a multitude of gas inlets
52
that pass through holes
54
in the furnace floor
38
, the floor insulation layer
36
, and the susceptor floor
28
.
U.S. Pat. No. 6,162,298 further describes a gas preheater
56
resting on the susceptor floor
28
and including a multitude of stacked perforated plates
58
that are spaced from other by a spacing structure
60
. Each plate
58
is provided with an array of perforations that are horizontally shifted from the array of perforations of the adjacent plate
58
. This causes the reactant gas to pass back and forth through the plates, which diffuses the reactant gas within the preheater
56
and increases convective heat transfer to the gas from the perforated plates
58
. A multitude of porous substrates
62
, for example brake disks, are stacked within the furnace
10
inside the susceptor
26
on fixtures (not shown).
Further, U.S. Pat. No. 6,162,298 is directed toward preventing gas leakage around the gas inlet
52
extending through the hole
54
in the susceptor floor
28
in the CVD/CVI furnace
10
. The method and apparatus seal the gas inlet
52
to the susceptor floor
28
with sufficient intimacy to block leakage of gas through the hole
54
around the gas inlet
52
while allowing the gas inlet
52
to cyclically translate through the hole
54
, as indicated by arrow
55
, due to thermal expansion and contraction induced by thermal cycles in the CVD/CVI furnace
10
.
Reactant gas entry through the gas inlets
52
is diffused within the preheater
56
and eventually reaches the porous substrates
62
. However, reactant gas leaving the gas inlets
52
follows a tortuous path as it travels back and forth through the plates
58
.
SUMMARY OF THE PRESENT INVENTION
The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.
The present invention, in part, is a recognition that current CVD/CVI process time is lengthy and results in considerable expense. The present invention provides a CVD/CVI method and apparatus that reduces process time, ensures efficient use of reactant gases, and permits an increase in process output.
The present invention, in part, is a recognition that reactant gas, such as densification gas, delivered directly to target carbon parts, will greatly improve process time.
The present invention, in part, provides a gas inlet port assembly for a CVD/CVI furnace having a furnace compartment and a CVD/CVI process apparatus with a plurality of holes, the gas inlet port assembly comprising a plurality of gas inlet ports delivering process gas to the furnace compartment; and a plurality of flow direction nozzles positioned between the holes of the CVD/CVI process apparatus and the gas inlet ports.
The present invention, also in part, provides a flow direction nozzle assembly for a CVD/CVI furnace, the flow direction nozzle assembly comprising a flow direction nozzle including a gas inlet port sealing portion; a support shoulder; and a nozzle portion.
The present invention, also in part, provides a method for sealing gas inlet ports for delivering a process gas in a CVD/CVI furnace, the method comprising positioning flow direction nozzles along upper lips of the gas inlet ports; loading a CVD/CVI process apparatus having a plurality of gas inlet holes into the furnace; sealingly engaging the flow direction nozzles to the gas inlet holes of the process apparatus to create a gas path-directing, fluid seal.
Advantages of the present invention will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 5359148 (1994-10-01), Okase et al.
patent: 5368648 (1994-11-01), Sekizuka
patent: 5480678 (1996-01-01), Rudolph et al.
patent: 5562947 (1996-10-01), White et al.
patent: 5746834 (1998-05-01), Hanley
patent: 5746875 (1998-05-01), Maydan et al.
patent
Jonnalagadda Rajanikant
Miller Brian J.
Honeywell International , Inc.
Lund Jeffrie R.
Palguta Larry J.
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