Patent Description:
Chemical vapor infiltration and deposition (CVI/CVD) is a known process for making composite structures such as carbon/carbon brake disks. The CVI/CVD process typically used for making carbon/carbon brake disks may involve passing a reactant gas or gas mixture (e.g., methane, propane, etc.) around heated porous structures (e.g., carbonized preforms) with a pressure differential driving the gas mixture into the porous structures. The gas enters into the porous structures, driven by pressure gradients, and undergoes a reaction such as thermal decomposition, hydrogen reduction, co-reduction, oxidation, carbonization, or nitridation to deposit a binding matrix.

Depending on CVI/CVD methodology and conditions, the porous structure may not densify at a uniform rate across the thickness of a porous structure, may not form a desired microstructure, and may be associated with long processing times. Thus, creation of uniformly densified porous structures may be impaired using conventional systems and methods. <CIT> discloses annular furnace spacers and a method for using the same. <CIT> discloses slotted seal plates and slotted performs for chemical vapor deposition densification.

The present disclosure encompasses and/or embodies a seal plate for disposition in a chemical vapor infiltration and deposition chamber. The seal plate may include a plurality of channels that extend completely through the seal plate. Such a plurality of channels may include a plurality of first channels, along with a plurality of second channels.

The seal plate may be in the form of a thin structure, with a maximum thickness being about <NUM>" (<NUM>) in various embodiments and about <NUM>" (<NUM>) in various embodiments. Any appropriate material or combination of materials may be utilized for the seal plate, including without limitation Carbon/Carbon (C/C), Silicon Carbide (SiC) or other refractory type materials that can withstand CVD temperatures. A body of the seal plate may include a plurality of fibers, such as carbon fibers, fiber-reinforced silicon carbide (SiC), Grafoil® (UCAR graphite based material), or any combination thereof. The seal plate may be densified by CVI/CVD.

The seal plate has an opening (e.g., centrally disposed). An inner perimeter of the seal plate may define a boundary of this opening, and an outer perimeter may be spaced (e.g., outwardly) from this inner perimeter. Such an inner perimeter and outer perimeter for the seal plate may be concentrically disposed, such that the outer perimeter may be characterized as being disposed radially outwardly from the inner perimeter.

A plurality of first channels extend through the seal plate. What is characterized as a first end of these first channels may be spaced outwardly from the above-noted inner perimeter of the seal plate, while what may be characterized as a second end of these first channels may be spaced inwardly from the above-noted outer perimeter of the seal plate, with the first end of each of the first channels being positioned closer to the inner perimeter than their corresponding second end. The first end of each of the first channels may be disposed a common distance from the inner perimeter, the second end of each of the first channels may be disposed a common distance from the outer perimeter, or both. Various embodiments has/have the width of each first channel progressively increasing proceeding from its corresponding first end to its corresponding second end (e.g., increasing at a constant rate). Each first channel may have a minimum width, proceeding along its corresponding length dimension, of about <NUM>" (<NUM>) in various embodiments. A centerline of each of the plurality of first channels (e.g., that extends from a first end to a corresponding second end of a given first channel) may be disposed along a radius extending from a center of the seal plate.

A plurality of second channels extend through the seal plate. What is characterized as a first end of these second channels may be spaced outwardly from the above-noted inner perimeter of the seal plate, while what may be characterized as a second end of these second channels may be spaced inwardly from the above-noted outer perimeter of the seal plate, with the first end of each of the second channels being positioned closer to the inner perimeter than their corresponding second end. The first end of each of the second channels may be disposed a common distance from the inner perimeter, the second end of each of the second channels may be disposed a common distance from the outer perimeter, or both. Various embodiments has/have the width of each second channel progressively increasing proceeding from its corresponding first end to its corresponding second end (e.g., increasing at a constant rate). Each second channel may have a minimum width, proceeding along its corresponding length dimension, of about <NUM>" (<NUM>) in various embodiments. A centerline of each of the plurality of second channels (e.g., that extends from a first end to a corresponding second end of a given second channel) may be disposed along a radius extending from a center of the seal plate.

At least one second channel is disposed between each adjacent pair of first channels. Various embodiments has/have a single second channel being disposed between each adjacent pair of first channels. The plurality of first channels may be characterized as being offset in a radial dimension relative to each of the plurality of second channels.

The first end of each first channel is disposed closer to the inner perimeter of the seal plate than the first end of each second channel. The second end of each second channel may be disposed closer to the outer perimeter of the seal plate than the second end of each first channel. The width of the first end of each first channel may be greater than the width of the first end of each second channel. The width of the second end of each first channel may be greater than the width of the second end of each second channel.

The seal plate include both an inner annulus and an outer annulus. Each channel that extends through the seal plate may extend from the inner annulus to the outer annulus. None of the channels used by the seal plate extend into the inner annulus or the outer annulus in various embodiments (e.g., the inner annulus, the outer annulus, or both may be free of one or more openings, one or more slots that extend partially through the seal plate, and/or may be free of one or more channels or other apertures that extend completely through the seal plate). A minimum width of the inner annulus is about <NUM>" (<NUM>) in various embodiments. A minimum width of the outer annulus is about <NUM>" (<NUM>) in various embodiments.

The seal plate is characterized as including an upper surface and an oppositely disposed lower surface, the distance between which is characterized as defining a thickness of the seal plate. One or alignment features may be included on at least one of the upper and lower surfaces of the seal plate, for instance to facilitate positioning a preform thereon. An inner alignment feature may be included on at least one of the upper and lower surfaces of the seal plate (e.g., such that a preform positioned on the seal plate is not disposed inwardly of such an alignment feature). An outer alignment feature may be included on at least one of the upper and lower surfaces of the seal plate (e.g., such that a preform positioned on the seal plate is not disposed outwardly of such an alignment feature). Any such inner alignment feature, any such outer alignment feature, or both may be in the form of a mark, groove, or the like. When both an inner alignment feature and an outer alignment feature are utilized, these alignment features may be concentrically disposed relative to one another, including in relation to an inner perimeter and/or an outer perimeter of the seal plate.

A preform stack for disposition in a chemical vapor infiltration and deposition chamber may include a pair of the above-noted seal plates, with a preform being disposed between and engaged by these seal plates. At least part of each first channel used by these seal plates may extend inwardly beyond an inner perimeter of the preform, and may define an inlet for introducing a gaseous medium into the corresponding first channel. One or more inner alignment features may be utilized to realize such a positioning. At least part of each second channel used by the seal plates may extend outwardly beyond an outer perimeter of the preform, and may define an outlet for allowing a gaseous medium to exit the corresponding second channel. One or more inner alignment features may be utilized to realize such a positioning. A chemical vapor infiltration and deposition chamber may be pressurized such that a gaseous medium enters each first channel through a corresponding and above-described inlet, and such that a gaseous medium exits each second channel through a corresponding and above-described outlet (e.g., a high pressure region in the chemical vapor infiltration and deposition chamber may be disposed radially inward of a low pressure region in the chemical vapor infiltration and deposition chamber, including where such a low pressure region corresponds with/includes the above-described opening in each seal plate within the preform stack).

Various aspects are also addressed by the following paragraphs and in the noted combinations:
A seal plate disposable between a pair of preforms in a chemical vapor infiltration and deposition chamber, comprising:.

The body may comprise a plurality of fibers selected from the group consisting of carbon, silicon carbide, or any combination thereof.

The inner perimeter and said outer perimeter may each be circular and concentrically disposed.

The first end of each said first channel may be disposed a common distance from said inner perimeter.

The second end of each said first channel may be disposed a common distance from said outer perimeter.

The first end of each said second channel may be disposed a common distance from said inner perimeter.

The second end of each said second channel may be disposed a common distance from said outer perimeter.

The width of each said first channel progressively may increase proceeding from its corresponding said first end to its corresponding said second end.

The width of each said first channel may increase at a constant rate proceeding from its corresponding said first end to its corresponding said second end.

The width of each said second channel may progressively increase proceeding from its corresponding said first end to its corresponding said second end.

The width of each said second channel may increase at a constant rate proceeding from its corresponding said first end to its corresponding said second end.

The first end of each said first channel may be closer to said inner perimeter than said first end of each said second channel.

The second end of each said second channel may be closer to said outer perimeter than said second end of each said first channel.

The width of said first end of each said first channel may be greater than a width of said first end of each said second channel.

The width of said second end of each said first channel may be greater than a width of said second end of each said second channel.

The thickness of said body may be no more than about <NUM>" (<NUM>).

The centerline of each of said plurality of first channels and each of said plurality of second channels may be disposed along a separate radius.

The at least one said second channel may be disposed between each adjacent pair of said first channels.

One said second channel may be disposed between each adjacent pair of said first channels.

Said body may further comprise an inner annulus and an outer annulus, wherein each of said plurality of first channels and each of said plurality of second channels are located entirely between said inner annulus and said outer annulus.

A minimum width of said inner annulus may be about <NUM>" (<NUM>).

A minimum width of said outer annulus may be about <NUM>" (<NUM>).

A minimum width of said first end of each said first channel may be about <NUM>" (<NUM>).

The width of said first end of each said first channel may be within a range of about <NUM>" (<NUM>) to about <NUM>" (<NUM>).

The seal may further comprise an inner alignment feature on said upper surface and an outer alignment feature on said upper surface.

The inner alignment feature may comprise at least one first alignment groove and wherein said outer alignment feature comprises at least one second alignment groove.

The first alignment groove may be disposed outwardly of said first end of each said first channel and intersects a corresponding adjacent pair of said first channels.

Each said second alignment groove may be disposed inwardly of said second end of each said second channel and may intersect a corresponding adjacent pair of said second channels.

A preform assembly is described comprising a preform, a first said seal plate, and a second said seal plate, wherein said preform is disposed between and contacts each of said first said seal plate and said second said seal plate, wherein an inner perimeter of said preform is aligned with said inner alignment feature, and wherein an outer perimeter of said preform is aligned with said outer alignment feature.

A chemical vapor infiltration and deposition chamber is described comprising a first said seal plate, a second said seal plate and a preform disposed between and contacting each of wherein said first said seal plate and said second said seal plate.

The chemical vapor infiltration and deposition chamber is described, wherein a high pressure side of said chemical vapor infiltration and deposition chamber is associated with said inner perimeter of each of said first said seal plate and said second said seal plate, and wherein a low pressure side of said chemical vapor infiltration and deposition chamber is associated with said outer perimeter of each of said first said seal plate and said second said seal plate.

The chemical vapor infiltration and deposition chamber is described, wherein said first channels comprise inlets channels and said second channels comprise outlet channels.

A preform stack for disposition in a chemical vapor infiltration and deposition chamber is described, comprising:.

The preform may comprise a plurality of first fibers.

The body may comprise a plurality of second fibers.

A width of each said first channel may progressively increase proceeding from its corresponding said first end to its corresponding said second end.

A width of each said first channel may increases at a constant rate proceeding from its corresponding said first end to its corresponding said second end.

A width of said first end of each said first channel may be within a range of about <NUM>" (<NUM>) to about <NUM>" (<NUM>).

The preform stack may further comprise an alignment feature on said upper surface.

Said body may further comprise a plurality of second channels that extend completely through said thickness of said body
proceeding from said upper surface to said lower surface, wherein a first end of each second channel of said plurality of second channels is spaced outwardly from said inner perimeter, wherein a second end of each said second channel is spaced inwardly from said outer perimeter, and wherein said first end of each said second channel is positioned closer to said inner perimeter than its corresponding said second end.

Each of said plurality of first channels may be different from each of said plurality of second channels.

Said first end of each said second channel may be disposed a common distance from said inner perimeter.

Said second end of each said second channel may be disposed a common distance from said outer perimeter.

A width of each said second channel may progressively increase proceeding from its corresponding said first end to its corresponding said second end.

Said width of each said second channel may increase at a constant rate proceeding from its corresponding said first end to its corresponding said second end.

Said first end of each said first channel may be closer to said inner perimeter than said first end of each said second channel.

Said second end of each said second channel may be closer to said outer perimeter than said second end of each said first channel.

A width of said first end of each said first channel may be greater than a width of said first end of each said second channel.

A width of said second end of each said first channel may be greater than a width of said second end of each said second channel.

A centerline of each of said plurality of first channels and each of said plurality of second channels may be disposed along a separate radius.

At least one said second channel may be disposed between each adjacent pair of said first channels.

Said first channels may extend beyond an inner perimeter of said preform and said second channels may extend beyond an outer perimeter of said preform.

Said first end of each said first channel may be disposed inwardly of an inner perimeter of said preform and a remainder of each said first channel accesses one of said upper preform surface and said lower preform surface, wherein said second end of each said second channel may be disposed outwardly of an outer perimeter of said preform and a remainder of each said second channel accesses one of said upper preform surface and said lower preform surface.

Said body may further comprise an inner annulus and an outer annulus, wherein each of said plurality of first channels and each of said plurality of second channels may be located entirely between said inner annulus and said outer annulus.

The preform stack may further comprise an inner alignment feature on said upper surface and an outer alignment feature on said upper surface.

Said inner alignment feature may comprise at least one first alignment groove and said outer alignment feature may comprise at least one second alignment groove.

Each said first alignment groove may be disposed outwardly of said first end of each said first channel and may intersect a corresponding adjacent pair of said first channels.

An inner perimeter of said preform may be aligned with said inner alignment feature and an outer perimeter of said preform may be aligned with said outer alignment feature.

The preform stack may further comprise:
a second said preform, wherein said first seal plate is disposed between and engages each of said preform and said second said preform, where said preform closes one side of a first length portion of each of said plurality of first channels and said second said preform closes an opposite side of said first length portion of each of said plurality of first channels.

For the preform stack of any of paragraphs <NUM>-<NUM>, said thickness of said body may be no more than about <NUM>" (<NUM>).

A method of processing a preform is described, comprising the steps of:.

Said preform may comprise an inner perimeter and an outer perimeter, and wherein said first direction is toward said outer perimeter of said preform.

The method may further comprise
introducing said gaseous medium into an inlet zone of said chamber that is located inwardly of said inner perimeter of said preform.

The first direction may be toward an exit zone that is at a lower pressure than said inlet zone and that is located outwardly of said inlet zone.

Each of said first and second seal plates may comprise an interior opening, an outer perimeter, and an inner perimeter that defines a boundary of said interior opening, wherein said inlet zone comprises said interior opening of each of said first and second seal plates.

The method may further comprise:
disposing a second said preform in said chamber, wherein said first seal plate is disposed between and engages each of said preform and said second said preform.

The method may further comprise:
simultaneously exposing a portion of each of said preform and said second said preform to said gaseous medium within each of said plurality of first channels of said first seal plate.

The method may further comprise:
introducing said gaseous medium into said plurality of first channels of each of said first and second seal plates through a first end portion of each of said plurality of first channels that extends inwardly beyond said preform.

The method may further comprise:
providing an outlet for said gaseous medium between each adjacent pair of said plurality of channels of said first and second seal plates.

The outlet may comprise a plurality of second channels that are spaced relative to each of said plurality of first channels.

The method may further comprise:
exiting said gaseous medium from said preform through a second end portion of each of said plurality of second channels that extends outwardly beyond said preform.

Referring to <FIG>, an exemplary fixture <NUM> in a chemical vapor infiltration (CVI) vessel is shown for pressure gradient CVI in a stack of porous structures <NUM>, in accordance with various embodiments. Porous structures <NUM> may have "OD" (outside diameter) seal plates <NUM> disposed around the outside diameter of porous structures <NUM>. Porous structures <NUM> may also have "ID" (inside diameter) seal plates <NUM> disposed around the inside diameter of porous structures <NUM>. The OD seal plates <NUM> may have an inside diameter <NUM> slightly less than the porous structure outside diameter <NUM>, and an outside diameter <NUM> that may be generally coterminous with the porous structure outside diameter <NUM>. The ID seal plates <NUM> may have an outside diameter <NUM> slightly greater than the porous structure inside diameter <NUM>, and an inside diameter <NUM> that may be generally coterminous with the porous structure inside diameter <NUM>. With ID seal plates <NUM>, the porous structure outside diameter <NUM> may be greater than the outside diameter <NUM> of the ring like ID seal plate <NUM>. Seal plate <NUM> and seal plate <NUM> may be disposed between porous structures <NUM> to provide spacing.

In various embodiments, seal plates <NUM> and seal plates <NUM> may provide sealing between external volume <NUM> and internal volume <NUM>. A pressure gradient may be maintained between external volume <NUM> and internal volume <NUM> to encourage gas <NUM> to travel from internal volume <NUM> through porous structures <NUM>. Gas <NUM> moves through porous structures <NUM> from internal volume <NUM> to external volume <NUM> and exits from vessel <NUM> through a port <NUM>. As gas <NUM> moves through porous structures <NUM>, gas deposits may densify porous structures <NUM>.

The porous structure <NUM> may comprise at least one of carbon, silicon carbide, silicon nitride, boron carbide, aluminum nitride, titanium nitride, boron nitride, zirconia, SiCxNy (wherein x is a number in the range from about zero to about <NUM>, and y is a number in the range from about zero to about <NUM>/<NUM>), silica, alumina, titania (TiO2), and a combination of at least two of the foregoing. Prior to densification, the porous structure may be referred to as a preform. A preform for use in making a carbon/carbon composite, such as a carbon/carbon disk brake, may be referred to as a carbonized preform.

A porous structure may comprise any porous structure derived from a fibrous material such as carbon fibers, silicon carbide fibers, and the like. The carbon fibers may be derived from polyacrylonitrile, rayon (synthetic fiber derived from cellulose), pitch, and the like. The fibrous material may be in the form of a woven, braided or knitted fabric or a needled felt. The fibrous material may be in the form of chopped carbon fibers molded to form a preform. Prior to the densification process, the fibrous material may be formed into a preform having any desired shape or form.

The porous structure may be in the form of a disk having any shape such as, for example, a polygon, a cylinder, a triangle, square, rectangle, pentagon, hexagon, octagon, and the like. In addition, the porous structure may have an irregular form.

A seal plate in accordance with various embodiments is illustrated in <FIG> and is identified by reference numeral <NUM>. Generally, this seal plate <NUM> may be disposed between an adjacent pair of porous structures <NUM> or preforms within the chemical vapor infiltration and deposition vessel <NUM> shown in <FIG>. The seal plate <NUM> may be in the form of a body formed from any appropriate material or combination of materials (e.g., Carbon/Carbon Composite). A plurality of fibers of any appropriate type (e.g., carbon, SiC) may be distributed throughout the body of the seal plate <NUM>.

The seal plate <NUM> includes an upper surface <NUM> and an oppositely disposed lower surface <NUM> that are spaced from one another to define a thickness for the seal plate <NUM>. An opening <NUM> extends completely through an interior portion of the seal plate <NUM> to define an inner perimeter <NUM>. Stated another way, the inner perimeter <NUM> may be characterized as defining a boundary for the opening <NUM>. This opening <NUM> may define a corresponding portion of the above-noted internal volume <NUM> when incorporated by the chemical vapor infiltration and deposition vessel of <FIG>.

An outer perimeter <NUM> of the seal plate <NUM> is disposed outwardly of the inner perimeter <NUM>. The inner perimeter <NUM> and outer perimeter <NUM> may be circular, may be concentrically disposed relative to a center <NUM> of the seal plate <NUM>, or both.

A plurality of first channels <NUM> extend completely through the thickness of the seal plate <NUM> (e.g., each first channel <NUM> extends from the upper surface <NUM> of the seal plate <NUM> to the lower surface <NUM> of the seal plate <NUM>) and are disposed in spaced relation to one another. Each first channel <NUM> may be characterized as including a first end <NUM> and a second end <NUM>. The spacing between the first end <NUM> and the second end <NUM> of each first channel <NUM> may be characterized as coinciding with a length dimension of the corresponding first channel <NUM>. In various embodiments, a centerline <NUM> that extends between the first end <NUM> and the second end <NUM> of each first channel <NUM> is disposed along a radius extending from the center <NUM>.

The first end <NUM> of each first channel <NUM> is spaced outwardly of the inner perimeter <NUM>, and as such may be characterized as being located between the inner perimeter <NUM> and its corresponding second end <NUM>. Each first end <NUM> may be characterized as being positioned closer to the inner perimeter <NUM> that its corresponding second end <NUM>. The second end <NUM> of each first channel <NUM> is spaced inwardly of the outer perimeter <NUM>, and as such may be characterized as being located between the outer perimeter <NUM> and its corresponding first end <NUM>. Each second end <NUM> may be characterized as being positioned closer to the outer perimeter <NUM> that its corresponding first end <NUM>.

In various embodiments, each first channel <NUM> is wider at its corresponding second end <NUM> compared to its corresponding first end <NUM> (e.g., the width dimension being orthogonal to the noted length dimension of the first channel <NUM>). In various embodiments, the width of each first channel <NUM> progressively increases proceeding from its corresponding first end <NUM> to its corresponding second end <NUM>. This increase in width regarding the first channels <NUM> may be continuous, may be at a constant rate, or both, proceeding along the length dimension of the corresponding first channel <NUM>. A minimum width of each first channel <NUM> at its corresponding first end <NUM> is about <NUM>" (<NUM>) in various embodiments, and is within a range from about <NUM>" (<NUM>) to about <NUM>" (<NUM>) in various embodiments.

The various first channels <NUM> may be disposed in equally-spaced relation to one another (e.g., the first channels <NUM> may be symmetrically disposed relative to/about the center <NUM> of the seal plate <NUM>). A common spacing may be used between the inner perimeter <NUM> and the first end <NUM> of each first channel <NUM>. A common spacing may be used between the outer perimeter <NUM> and the second end <NUM> of each first channel <NUM>.

A plurality of second channels <NUM> extend completely through the thickness of the seal plate <NUM> (e.g., each second channel <NUM> extends from the upper surface <NUM> of the seal plate <NUM> to the lower surface <NUM> of the seal plate <NUM>) and are disposed in spaced relation to one another. The plurality of first channels <NUM> may be characterized as being different in one or more respects than the plurality of second channels <NUM>. At least one second channel <NUM> is disposed between each adjacent pair of first channels <NUM> in various embodiments (e.g., a single second channel <NUM> in <FIG>).

Each second channel <NUM> may be characterized as including a first end <NUM> and a second end <NUM>. The spacing between the first end <NUM> and the second end <NUM> of each second channel <NUM> may be characterized as coinciding with a length dimension of the corresponding second channel <NUM>. In various embodiments, a centerline <NUM> that extends between the first end <NUM> and the second end <NUM> of each second channel <NUM> is disposed along a radius emanating from the center <NUM>.

The first end <NUM> of each second channel <NUM> is spaced outwardly of the inner perimeter <NUM>, and as such may be characterized as being located between the inner perimeter <NUM> and its corresponding second end <NUM>. Each first end <NUM> may be characterized as being positioned closer to the inner perimeter <NUM> that its corresponding second end <NUM>. The second end <NUM> of each second channel <NUM> is spaced inwardly of the outer perimeter <NUM>, and as such may be characterized as being located between the outer perimeter <NUM> and its corresponding first end <NUM>. Each second end <NUM> may be characterized as being positioned closer to the outer perimeter <NUM> that its corresponding first end <NUM>.

In various embodiments, each second channel <NUM> is wider at its corresponding second end <NUM> compared to its corresponding first end <NUM> (e.g., the width dimension being orthogonal to the noted length dimension of the second channel <NUM>). In various embodiments, the width of each second channel <NUM> progressively increases proceeding from its corresponding first end <NUM> to its corresponding second end <NUM>. This increase in width regarding the second channels <NUM> may be continuous, may be at a constant rate, or both, proceeding along the length dimension of the corresponding second channel <NUM>. A minimum width of each second channel <NUM> at its corresponding first end <NUM> is about <NUM>" (<NUM>) in various embodiments, and is within a range from about <NUM>" (<NUM>) to about <NUM>" (<NUM>) in various embodiments.

The various second channels <NUM> may be disposed in equally-spaced relation to one another (e.g., the second channels <NUM> may be symmetrically disposed relative to/about the center <NUM> of the seal plate <NUM>). A common spacing may be used between the inner perimeter <NUM> and the first end <NUM> of each second channel <NUM>. A common spacing may be used between the outer perimeter <NUM> and the second end <NUM> of each second channel <NUM>.

The first end <NUM> of each first channel <NUM> may be closer to the inner perimeter <NUM> than the first end <NUM> of each second channel <NUM>. The second end <NUM> of each second channel <NUM> may be closer to the outer perimeter <NUM> than the second end <NUM> of each first channel <NUM>. The width of each first channel <NUM> at its first end <NUM> may be greater than the width of each second channel <NUM> at its corresponding first end <NUM>. The width of each first channel <NUM> at its second end <NUM> may be greater than the width of each second channel <NUM> at its corresponding second end <NUM>.

The seal plate <NUM> includes an inner annulus <NUM> and an outer annulus <NUM> that are spaced from one another (e.g., in a radial dimension or relative to the center <NUM> of the seal plate <NUM>). Each first channel <NUM> and each second channel <NUM> is disposed entirely between the inner annulus <NUM> and the outer annulus <NUM> in various embodiments. Stated another way none of the first channels <NUM>, nor none of the second channels <NUM>, extend into either the inner annulus <NUM> or the outer annulus <NUM> in various embodiments. The inner annulus <NUM> and the outer annulus <NUM> contribute to/enhance the structural integrity of the seal plate <NUM>.

The inner annulus <NUM> and the outer annulus <NUM> may be concentrically disposed relative to one another. One characterization is that the inner annulus <NUM> extends from the inner perimeter <NUM> to the location corresponding with first end <NUM> of each of the plurality of first channels <NUM>. Another characterization is that the outer annulus <NUM> extends from the outer perimeter <NUM> to the location corresponding with the second end <NUM> of each of the plurality of second channels <NUM>. A minimum width of the inner annulus <NUM> is about <NUM>" (<NUM>) in one more embodiments (e.g., measured along a radius emanating from the center <NUM> of the seal plate <NUM>). A minimum width of the outer annulus <NUM> is about <NUM>" (<NUM>) in one more embodiments (e.g., measured along a radius emanating from the center <NUM> of the seal plate <NUM>). In various embodiments, the thickness of the seal plate <NUM> is no more than about <NUM>" (<NUM>).

A variation of the seal plate <NUM> of <FIG> is presented in <FIG> and is identified by reference numeral <NUM>'. Corresponding components between the seal plate of <FIG> and the seal plate <NUM>' of <FIG> are identified by the same reference numerals, and the discussion presented above remains equally applicable unless otherwise noted to the contrary. The seal plate <NUM>' includes a plurality of inner alignment grooves <NUM> and a plurality of outer alignment grooves <NUM> that are each formed on the upper surface <NUM> of the seal plate <NUM>' (although such alignments grooves <NUM>, <NUM> could be formed on both the upper surface <NUM> and the lower surface <NUM> of the seal plate <NUM>'). The inner alignment grooves <NUM> may be characterized as being collectively concentrically disposed relative to the outer alignment grooves <NUM>. Each of the alignment grooves <NUM>, <NUM> may be of any appropriate configuration.

As is shown in <FIG>, each inner alignment groove <NUM> intersects an adjacent pair of first channels <NUM> at a location that is spaced outwardly from the first end <NUM> of each such first channel <NUM>. Although the inner alignment grooves <NUM> are illustrated as being continuous proceeding between each adjacent pair of first channels <NUM>, such may not be required in each instance (e.g., the inner alignment groove <NUM> could be in the form of one or more segments that are spaced from one another proceeding between the corresponding adjacent pair of first channels <NUM>).

As is further shown in <FIG>, each outer alignment groove <NUM> intersects an adjacent pair of second channels <NUM> at a location that is spaced inwardly from the second end <NUM> of each such second channel <NUM>. Although the outer alignment grooves <NUM> are illustrated as being continuous proceeding between each adjacent pair of second channels <NUM>, such may not be required in each instance (e.g., the outer alignment groove <NUM> could be in the form of one or more segments that are spaced from one another proceeding between the corresponding adjacent pair of second channels <NUM>).

The inner alignment grooves <NUM> and the outer alignment grooves <NUM> facilitate the positioning of a preform <NUM> (e.g., in accordance with the porous structure <NUM> discussed above) on the seal plate <NUM>' and as shown in <FIG>. The preform <NUM> may include an upper preform surface <NUM> and a lower preform surface (that faces the seal plate <NUM>' in the view shown in <FIG>) that are oppositely disposed and spaced from one another (e.g., to define a thickness of the preform <NUM>). This preform <NUM> may further include an inner perimeter <NUM> and an outer perimeter <NUM> that are spaced from one another (e.g., in a radial dimension). The inner perimeter <NUM> and outer perimeter <NUM> may be concentrically disposed in various embodiments.

The combination of the preform <NUM> and the seal plate <NUM>' may be collectively referred to as a preform stack <NUM>. Another seal plate <NUM>' would typically be positioned on the upper preform surface <NUM> of the preform <NUM> in the <FIG> arrangement. The preform stack <NUM> may include any appropriate number of preforms <NUM>, with each adjacent pair of preforms <NUM> being disposed between and engaged by a pair of seal plates <NUM>'. In any case, the preform stack <NUM> may be disposed within the chemical vapor infiltration and deposition vessel <NUM> shown <FIG>.

As shown in <FIG>, the outer perimeter <NUM> of the preform <NUM> is at least generally aligned with the outer alignment grooves <NUM> of the seal plate <NUM>', while the inner perimeter <NUM> of the preform <NUM> is at least generally aligned with the inner alignment grooves <NUM> of the seal plate <NUM>'. As such, a portion of each second channel <NUM> of the seal plate <NUM>' extends beyond the outer perimeter <NUM> of the preform <NUM> (in the direction of the outer perimeter <NUM> of the seal plate <NUM>') to define a plurality of outlet ports <NUM>, while a portion of each first channel <NUM> of the seal plate <NUM>' extends beyond the inner perimeter <NUM> of the preform <NUM> (in the direction of the inner perimeter <NUM> of the seal plate <NUM>') to define a plurality of inlet ports <NUM>. <FIG> and <FIG> illustrate the existence of the above-noted inlet ports <NUM> and outlet ports <NUM> for the case where the preform <NUM> is positioned on the seal plate <NUM> of <FIG> (where the seal plate <NUM> does not include the alignment features of the seal plate <NUM>').

A preform stack <NUM> in accordance with the foregoing may be disposed within the chemical vapor infiltration vessel <NUM> shown <FIG> for simultaneous processing of each preform <NUM> of the stack <NUM>. As a seal plate <NUM>' will be disposed between each adjacent pair of preforms <NUM> and engages each of these preforms <NUM>, gas that is within a given first channel <NUM> will simultaneously access a corresponding surface of both preforms <NUM> (e.g., an upper side of a given first channel <NUM> will be closed by one preform <NUM> (except for the ports <NUM>), while a lower side of the same first channel <NUM> will be closed by an opposing preform <NUM> (except for the ports <NUM>). The opening <NUM> of the various seal plates <NUM>' each define a portion of the internal volume <NUM> of the chemical vapor infiltration and deposition vessel <NUM> of <FIG> (along with the open space disposed inwardly of the inner perimeter <NUM> of each preform <NUM>). A pressure gradient may be maintained between the external volume <NUM> and the internal volume <NUM> of the chemical vapor infiltration and deposition vessel <NUM> to encourage gas <NUM> to travel from internal volume <NUM> through the various preforms <NUM>. Gas <NUM> moves through the preforms <NUM> from internal volume <NUM> to external volume <NUM> and exits from vessel <NUM> through port <NUM> of the vessel <NUM>. More specifically, gas <NUM> may enter each of the first channels <NUM> of the seal plate <NUM>' through the above-noted inlet ports <NUM> (first channels <NUM>), while gas <NUM> may exit each of the second channels <NUM> of the seal plate <NUM>' through the above-noted outlet ports <NUM> (second channels <NUM>). The profile of at least the plurality of first channels <NUM> is believed to enhance the distribution of the gas <NUM> throughout the preforms <NUM>, namely by the progressively increasing width of the first channels <NUM> proceeding in the direction of their corresponding second ends <NUM> based upon the higher pressure existing in the internal volume <NUM> versus the external volume <NUM>. The noted profile of the first channels <NUM> accounts for there being more reactive gas toward the inner perimeter <NUM> of the seal plates <NUM>' compared to toward the outer perimeter <NUM> of the seal plate <NUM>' for purposes of enhancing the distribution of gas <NUM> throughout the various preforms <NUM> (e.g., the width of the first channels <NUM> progressively increases proceeding from the inner perimeter <NUM> to the outer perimeter <NUM> of the various seal plates <NUM>' to account for the concentration of the gas <NUM> decreasing proceeding from the inner perimeter <NUM> to the outer perimeter <NUM> of the various seal plates <NUM>'). The seal plate <NUM> will function similarly to the seal plate <NUM>' except in relation to the alignment provided by the seal plate <NUM>'.

The seal plates <NUM>, <NUM>' provide a number of advantages. One is enhanced mechanical strength or a more robust structure, even when utilizing a thinner profile (e.g., a reduced thickness for the seal plates <NUM>, <NUM>' in accordance with the foregoing). Another is facilitating a more uniform densification of preforms <NUM> during chemical vapor infiltration and deposition, for instance by providing an increased gas flow through the first channels <NUM> (from their corresponding first ends <NUM> to their corresponding second ends <NUM>, and that may correspond with a first direction) based on one or more of the above-described features/characteristics. Although material may be deposited on the sidewalls of the first channels <NUM>, the sizing of the first channels <NUM> should increase the amount of time between which sidewalls of the first channels <NUM> will need to be cleaned or re-formed - to remove material that has been deposited on the sidewalls of the first channels <NUM> during chemical vapor infiltration and deposition. The first channels <NUM> and second channels <NUM> may also facilitate removal of the seal plates <NUM>, <NUM>' from the preform <NUM> due to the reduced contact area between the seal plates <NUM>, <NUM>' and the preform <NUM> (compared to a continuous flat surface or the like).

The foregoing description has been presented for purposes of illustration and description. Furthermore, the description is not intended to be limited to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are within the scope of the present disclosure.

Claim 1:
A seal plate (<NUM>) disposable between a pair of preforms in a chemical vapor infiltration and deposition chamber, comprising:
a body comprising an opening (<NUM>), an inner perimeter (<NUM>) that defines a boundary of said opening (<NUM>), an outer perimeter (<NUM>) spaced from said inner perimeter, an upper surface, and a lower surface that is spaced from said upper surface to define a thickness of said body;
a plurality of first channels (<NUM>) that extend completely through said thickness of said body, wherein a first end of each first channel of said plurality of first channels is spaced outwardly from said inner perimeter, wherein a second end of each said first channel is spaced inwardly from said outer perimeter, and wherein said first end of each said first channel is positioned closer to said inner perimeter than its corresponding said second end;
a plurality of second channels (<NUM>) that extend completely through said thickness of said body proceeding from said upper surface to said lower surface, wherein a first end of each second channel of said plurality of second channels is spaced outwardly from said inner perimeter, wherein a second end of each said second channel is spaced inwardly from said outer perimeter, and wherein said first end of each said second channel is positioned closer to said inner perimeter than its corresponding said second end;
wherein each of said plurality of first channels (<NUM>) is different from each of said plurality of second channels (<NUM>),
wherein the first end of each first channel of said plurality of first channels is closer to the inner perimeter than the first end of each second channel of said plurality of second channels, and
wherein the second end of each second channel of said plurality of second channels is closer to the outer perimeter than the second end of each first channel of said plurality of first channels.