Patent Description:
The disclosure relates to extrudate production, and more particularly to systems and methods for skin stiffening of wet extrudate by circumferential irradiation.

Ceramic extrudates are used in a wide variety of applications, such as substrates for automotive exhaust catalytic converters, particulate traps within diesel and gasoline engines, chemical filtration processes, and the like. Ceramic bodies produced by extrusion and having honeycomb cross-sectional shapes are frequently employed to provide a large filtration and/or catalytic surface area within a relatively small overall volume. The manufacturing process for extruded ceramic bodies typically includes producing wet extrudate of desired shape and dimensions using an extrusion apparatus, cutting the extrudate into sections, and transferring the cut sections to a kiln for firing to produce a dry fired body.

It is important to maintain the shape of the wet extrudate material upon leaving an extrusion die through production into a fired product. Further, larger products typically require further processing (e.g., contouring, applied skin processing, etc.) to mitigate quality issues resulting from slump of the wet extrudate material, which can significantly add to manufacturing costs.

Conventional methods that have been developed to attempt to strengthen wet extrudate material prior to firing have suffered from inadequate results, due to non-uniform stiffening or other complications. For example, radio frequency and microwave radiation are generally volumetric energy sources and deposit energy in modes that may produce hot and cold spots, thereby which may result in distortion of cells within wet extrudate material. Other methods such as heating by clamshell irradiation or impingement of hot air on an exterior of wet extrudate may suffer from lack of uniformity, and may also heat the skin of wet extrudate up to <NUM>, which may lead to stiffness by thermogelation (instead of drying) such as due to the presence of an organic binder, and such stiffness increase may be temporary and subject to decrease when the extrudate is cooled.

<CIT> discloses an extrusion system comprising: an extrusion die comprising an outlet and configured to continuously form wet extrudate material comprising a honeycomb cross-section; at least one device having a hollow interior, positioned downstream of the outlet in a direction of travel of the wet extrudate material, arranged in a generally cylindrical shape around a perimeter of the wet extrudate material; and an extrudate support channel configured to receive the stiffened wet extrudate material following passage of the wet extrudate material through the hollow interior of the at least one device.

<CIT>, <CIT>, <CIT>, <CIT> and <CIT> disclose other prior art.

An extrusion system according to certain aspects includes at least one infrared emitting device arranged in a generally cylindrical shape with a hollow interior. The at least one infrared emitting device is positioned downstream of an outlet of an extrusion die to irradiate a perimeter of wet extrudate material in a uniform manner to form stiffened wet extrudate material before such material is received by an extrudate support channel. The at least one infrared emitting device generally uniformly stiffens the skin of the wet extrudate material to resist mechanical deformation of the extrudate material during subsequent handling steps. Such skin stiffening allows for increased tolerance of handling forces and permits extrusion of softer wet extrudate material without compromising the same of a fired ceramic product, among other advantages.

The present disclosure provides an extrusion system according to claim <NUM>.

The at least one infrared emitting device is configured to produce infrared emissions having at least one peak emission wavelength and at least one full-width, half-maximum emission wavelength range. Further, the wet extrudate material includes a plurality of constituents each having an absorption spectrum having at least one peak absorption wavelength and at least one full-width, half-maximum absorption wavelength range. Further, the at least one full-width, half-maximum emission wavelength range includes at least one wavelength value within <NUM> micrometer of a wavelength of the at least one full-width, half-maximum absorption wavelength range of the absorption spectrum of at least one constituent of the plurality of constituents. In certain embodiments, the at least one peak emission wavelength includes at least one of <NUM> or <NUM>. In certain embodiments, the at least one peak absorption wavelength includes at least one of <NUM>, <NUM>, or <NUM>. In certain embodiments, the generally cylindrical shape of the at least one infrared emitting device includes an internal diameter of at least <NUM>. In certain embodiments, the at least one infrared emitting device includes at least one laser. In certain embodiments, the at least one infrared emitting device includes at least one lamp.

In certain embodiments, the at least one infrared emitting device includes a plurality of infrared emitting devices, and each infrared emitting device of the plurality of infrared emitting devices is configured to produce infrared emissions of a different peak emission wavelength and a different full-width, half-maximum emission wavelength range. In certain embodiments, the at least one infrared emitting device includes a plurality of infrared emitting devices including a first infrared emitting device and a second infrared emitting device positioned downstream of the first infrared emitting device in the direction of travel of the wet extrudate material. In certain embodiments, the first infrared emitting device and the second infrared emitting device are each arranged in a generally cylindrical shape, and the first and second infrared emitting devices are configured to irradiate the wet extrudate material with differing total radiant flux. In certain embodiments, the extrusion system is configured to irradiate the wet extrudate material with an intensity and duration selected to provide the stiffened wet extrudate material with a uniformly stiffened external surface and a non-stiffened core. In certain embodiments, the present disclosure relates to a stiffened wet extrudate material formed from the foregoing extrusion system. The stiffened wet extrudate material has a porous structure that includes a uniformly stiffened external surface and a non-stiffened core including a honeycomb cross-section.

The present disclosure further provides a method of forming a stiffened wet extrudate material according to claim <NUM>.

The infrared emissions include at least one peak emission wavelength and at least one full-width, half-maximum emission wavelength range corresponding to the at least one peak emission wavelength. Further, the wet extrudate material includes a plurality of constituents each having an absorption spectrum having at least one peak absorption wavelength and at least one full-width, half-maximum absorption wavelength range corresponding to the at least one peak absorption wavelength. Further, the at least one full-width, half-maximum emission wavelength range corresponding to the at least one peak emission wavelength includes at least one wavelength value within <NUM> micrometer of a wavelength of the at least one full-width, half-maximum absorption wavelength range corresponding to the at least one peak absorption wavelength of the absorption spectrum of at least one constituent of the plurality of constituents. In certain embodiments, the at least one peak emission wavelength includes at least one of <NUM> or <NUM>. In certain embodiments, the at least one peak absorption wavelength includes at least one of <NUM>, <NUM>, or <NUM>. In certain embodiments, the generally cylindrical shape of the at least one infrared emitting device includes an internal diameter of at least <NUM>. In certain embodiments, the at least one infrared emitting device includes at least one laser. In certain embodiments, the at least one infrared emitting device includes at least one lamp.

In certain embodiments, the at least one infrared emitting device includes a plurality of infrared emitting devices, and each infrared emitting device of the plurality of infrared emitting devices is configured to produce infrared emissions of a different peak emission wavelength and a different full-width, half-maximum emission wavelength range. In certain embodiments, the at least one infrared emitting device includes a plurality of infrared emitting devices including a first infrared emitting device and a second infrared emitting device positioned downstream of the first infrared emitting device in a direction of travel of the wet extrudate material. Also, the method further includes irradiating the wet extrudate material with a first radiant flux using the first infrared emitting device and irradiating the wet extrudate material with a second radiant flux using the second infrared emitting device, and the second radiant flux differs from the first radiant flux. In certain embodiments, uniformly irradiating the perimeter of the wet extrudate material further includes uniformly irradiating with an intensity and duration selected to provide the stiffened wet extrudate material with a uniformly stiffened external surface and a non-stiffened core.

Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain principles and operation of the various embodiments.

Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the drawing figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the drawing figures.

We have found that when producing ceramic extrudates having large diameters, thin walls, and/or large open frontal areas, wet extrudate material can be subject to an increased likelihood of mechanical deformation during post-extrusion handling. Such mechanical deformation may lead to decreased quality in fired products and even significant production losses. For example, slump of wet extrudate material during manufacturing may compromise the shape of the fired product, which may be important to meet isostatic strength specifications. Maintaining the shape of the wet extrudate material upon leaving an extrusion die through production into a fired product is therefore important.

<FIG> is a schematic top plan view of an extrusion system <NUM> including at least one infrared emitting device <NUM> proximate to an outlet of an extrusion apparatus <NUM> (which may also be referred to herein as an extruder). The extrusion system <NUM> also includes at least one sensor <NUM>, a cutting assembly <NUM> (which may also be referred to herein as a wet saw or wet saw assembly), and an extrudate support channel <NUM> arranged as part of a conveyor apparatus (e.g., including an air bearing surface enabling wet extrudate to be translated to a dryer tray <NUM> for subsequent transport to a kiln or other bulk drying apparatus) to produce a fired product (e.g., aluminum titanate, cordierite, other silica compositions, etc.).

The extrusion apparatus <NUM> has an extrusion die <NUM> including an outlet <NUM> and is configured to continuously form wet extrudate material <NUM>. The infrared emitting device <NUM> is positioned downstream of the outlet <NUM> in a direction of travel of the wet extrudate material <NUM>. The extrusion apparatus <NUM> is a horizontal extruder which horizontally extrudes the wet extrudate material <NUM>. In certain embodiments, the wet extrudate material <NUM> is a wet ceramic material. In certain embodiments, the wet extrudate material <NUM> is a wet ceramic material, and may include constituents such as aluminum titanate, mullite, talc, alumina, silica, clays, aluminum hydroxide, or any other suitable ceramic precursor material. In certain embodiments, the wet extrudate material <NUM> includes graphite, which has a high absorption of infrared emissions and thereby requires less power to stiffen.

The infrared emitting device <NUM> is configured to impart energy around an entire perimeter (e.g., circumference) of the wet extrudate material <NUM> to dry and uniformly stiffen the external surface (i.e., exterior, or skin) to set the shape of the wet extrudate material <NUM> upon leaving the extrusion die <NUM> and form stiffened wet extrudate material <NUM>. The extrusion system <NUM> irradiates the wet extrudate material <NUM> with an intensity and duration selected to form the stiffened wet extrudate material <NUM> with a uniformly stiffened external surface and a non-stiffened core. In certain embodiments, the stiffened wet extrudate material has a porous structure that includes a uniformly stiffened external surface and a non-stiffened core including a honeycomb cross-section.

An extrudate support channel <NUM> arranged as part of a conveyor apparatus is configured to receive the stiffened wet extrudate material <NUM> following passage of the wet extrudate material <NUM> through the infrared emitting device <NUM>. In certain embodiments, the extrudate support channel <NUM> may have a partial circular, ovular, or rectangular cross-section to guide the stiffened wet extrudate material <NUM>. The at least one sensor <NUM> is positioned between the infrared emitting device <NUM> and the wet saw assembly <NUM> to measure the moisture content of the stiffened wet extrudate material <NUM>. In other embodiments, the at least one sensor <NUM> may include at least one positioned between the outlet <NUM> of the extrusion die <NUM> and the infrared emitting device <NUM> to measure a characteristic (e.g., moisture content) of the wet extrudate material <NUM>. In other words, the at least one sensor <NUM> may be positioned upstream and/or downstream of the at least one infrared emitting device <NUM> in a direction of travel of the wet extrudate material <NUM> and/or the stiffened wet extrudate material <NUM>. As the infrared emitting device <NUM> dries a circumferential portion of the wet extrudate material <NUM>, the at least one sensor <NUM> provides feedback (e.g., real-time feedback) as to whether the wet extrudate material <NUM> and/or the stiffened wet extrudate material <NUM> is within acceptable specifications, particularly as to moisture content (e.g., to prevent overdrying), and especially for sensitive applications with narrow product specifications. In certain embodiments, a controller may be in electronic communication with the at least one sensor <NUM> and configured to adjust operating parameters of the infrared emitting device <NUM> (e.g., irradiation intensity), the extrusion apparatus <NUM> (e.g., the feed rate of the wet extrudate material <NUM>), and/or an optional humidifier apparatus (not shown) to at least partially rehydrate the wet extrudate material <NUM> and/or the stiffened wet extrudate material <NUM>, etc..

In certain embodiments, the at least one sensor <NUM> includes an optical sensor configured to sense a reflectance property (e.g., reflectance of electromagnetic radiation), an absorbance property (e.g., absorbance of electromagnetic radiation), and/or a temperature of the exterior surface of the wet extrudate material <NUM> and/or stiffened wet extrudate material <NUM>. In certain embodiments, the at least one sensor <NUM> includes at least one radio frequency sensor configured to quantify moisture content in one or more portions of the wet extrudate material <NUM> and/or stiffened wet extrudate material <NUM>.

The cutting assembly <NUM> cuts a portion from the stiffened wet extrudate material <NUM> to form a stiffened wet extrudate section <NUM> (which may also be referred to herein as a stiffened wet extrudate). In other words, the wet extrudate material <NUM> is extruded through the infrared emitting device <NUM> to form stiffened wet extrudate material <NUM>, which is then translated by the extrudate support channel <NUM> to the wet saw assembly <NUM>, which cuts the stiffened wet extrudate material <NUM> to form multiple stiffened wet extrudate sections <NUM>.

Once cut, a stiffened wet extrudate section <NUM> is translated by the extrudate support channel <NUM> (as part of a conveyor apparatus) to the dryer tray <NUM>. The extrudate support channel <NUM> may include an air bearing surface <NUM> over which the stiffened wet extrudate section <NUM> translates to promote low-friction movement of the stiffened wet extrudate section <NUM>.

<FIG> depict wet extrudate material <NUM> formed from the extrusion system of <FIG>. It is to be noted that the stiffened wet extrudate material <NUM> and the stiffened wet extrudate sections <NUM> have similar configurations and features. The wet extrudate material <NUM> has a first end <NUM> (e.g., front end), as well as a peripheral wall <NUM> having an external surface <NUM> (i.e., skin or outer surface, etc.) and a plurality of intersecting walls <NUM> within the peripheral wall <NUM>. The intersecting walls <NUM> form mutually adjoining cell channels <NUM> extending axially in direction "A" from the first end <NUM>. In certain embodiments, the wet extrudate material <NUM> has a honeycomb cross-section <NUM>. The wet extrudate material <NUM> may have a diameter of any size, including comparatively large sizes (e.g., diameters of <NUM> inches (<NUM>), <NUM> inches (<NUM>), or greater).

<FIG> are views of the infrared emitting device <NUM> of <FIG> irradiating the wet extrudate material <NUM> formed from the extrusion die <NUM> of the extrusion system <NUM>. For example, in certain embodiments, the wet extrudate material <NUM> is extruded at a rate of <NUM> in/s (<NUM>/s). The infrared emitting device <NUM> is configured to uniformly irradiate the external surface <NUM> (e.g., around the entire circumferential perimeter) of the wet extrudate material <NUM> to form stiffened wet extrudate material <NUM>. In certain embodiments, the infrared emitting device <NUM> can be retrofitted to existing systems and/or integrated into new systems, without the cost and complexity of other alternative systems (e.g., systems for delivering a ring of hot air to wet extrudate material). Further, the infrared emitting device <NUM> is relatively small and does not significantly add to the space required in the manufacturing of the stiffened wet extrudate sections <NUM>, which is advantageous in applications with limited space. The amount of energy emitted by the infrared emitting device <NUM> can be well controlled (e.g., patterned), unlike some other technologies (e.g., ring of hot air). However, it is noted that in certain embodiments, the infrared emitting device <NUM> can be used in combination with drying using a ring of hot air, such as for flash drying. In certain embodiments, the at least one infrared emitting device <NUM> includes an infrared lamp, one or more infrared lasers, infrared light emitting diodes, or other emitter types. In certain embodiments other electromagnetic emitters may be used (e.g., a microwave emitting device).

Referring to <FIG>, the peripheral wall <NUM> of the stiffened wet extrudate material <NUM> includes a stiffened outer portion <NUM> and a non-stiffened inner portion <NUM>. The depth of penetration D of the emissions of the infrared emitting device <NUM> into the peripheral wall <NUM> (and the intersecting walls <NUM>) may depend on the properties of the infrared emissions (e.g., intensity, duration, etc.) and/or the properties of the wet extrudate material <NUM>.

Referring to <FIG>, the extrudate support channel <NUM> is configured to receive the stiffened wet extrudate material <NUM> following passage of the wet extrudate material <NUM> through the infrared emitting device <NUM>. As the stiffened wet extrudate material <NUM> settles onto the air bearing surface <NUM> of the extrudate support channel <NUM>, the stiffened wet extrudate material <NUM> retains the original shape of the wet extrudate material <NUM> as it exits the extrusion die <NUM>.

Referring to <FIG>, the infrared emitting device <NUM> has a hollow interior <NUM> and is arranged in a generally cylindrical shape around a perimeter of the wet extrudate material <NUM>, such that the wet extrudate material <NUM> passes through the hollow interior <NUM> of the at least one infrared emitting device <NUM>. The infrared emitting device <NUM> includes a peripheral portion <NUM> and an inner surface <NUM> concentric with the peripheral portion <NUM>. In certain embodiments, the generally cylindrical shape of the at least one infrared emitting device <NUM> includes an internal diameter of at least <NUM> (e.g., <NUM>). In certain embodiments, a central axis of the infrared emitting device <NUM> is aligned with a central axis of the outlet <NUM> of the extrusion die <NUM>. In other words, the infrared emitting device <NUM> and the outlet <NUM> may share a common longitudinal axis.

The length (e.g., front to back) of the infrared emitting device <NUM> may be adjusted or selected depending on the desired duration of irradiation of the wet extrudate material <NUM> by the infrared emitting device <NUM>. It is noted that an irradiation duration is also determined by the feed rate of the wet extrudate material <NUM> through the outlet <NUM> of the extrusion die <NUM>.

Referring to <FIG>, in certain embodiments, the peripheral portion <NUM> includes a reflective coating to direct emissions inward toward the hollow interior <NUM> (and thereby the wet extrudate material <NUM>). As the infrared emitting device <NUM> is generally cylindrical, the wet extrudate material <NUM> is also generally cylindrical, and the infrared emitting device <NUM> and the wet extrudate material <NUM> are aligned along a common axis. The infrared emitting device <NUM> provides generally uniform emissions toward a center of the hollow interior <NUM>, which generally uniformly heats the wet extrudate material <NUM> in a circumferential band around the peripheral wall <NUM> of the wet extrudate material <NUM>.

Use of the infrared emitting device <NUM> is very precise, and is devoid of contact with the wet extrudate material <NUM>, only heating the surface of the wet extrudate material <NUM>. Accordingly, the infrared emitting device <NUM> avoids distorting cells or mechanically deforming the wet extrudate material <NUM>.

The stiffened periphery of the stiffened wet extrudate material <NUM> allows for increased tolerance of handling forces (e.g., contact with tray, gravity, acceleration forces, deceleration forces, etc.) with improved quality (i.e., without affecting the overall shape or internal configuration of the product), for example, as the stiffened wet extrudate section <NUM> translates from the air bearing surface <NUM> of the extrudate support channel <NUM> to the dryer tray <NUM>. Further, by stiffening the peripheral wall <NUM>, the wet extrudate material <NUM> can include greater water content and be extruded softer, thereby increasing longevity of life of extrusion die <NUM> and improving feed-rate of wet extrudate material <NUM>. By stiffening the peripheral wall <NUM> and maintaining shape of the wet extrudate material <NUM>, isostatic performance can also be improved (e.g., increased probability of reduced scatter in isostatic strength), even for products with thinner walls and larger open frontal areas. Stiffening the wet extrudate material <NUM> enables extrusion of larger size parts (e.g., greater than <NUM> inches (<NUM>)) using the horizontal extrusion process, while also eliminating the need for further processing steps (e.g., contouring, applied skin processes, etc.). This can significantly reduce manufacturing costs.

In certain embodiments, local humidity is controlled such that thermal gelation and drying can be separated. For example, a substrate can be dried at room temperature with low humidity or thermally gelled without drying in high humidity.

<FIG> are views comparing deformation results of cantilever tests performed on an unstiffened wet extrudate material <NUM> and a stiffened wet extrudate material <NUM>. Referring to <FIG>, as the unstiffened wet extrudate material <NUM> travels past an end <NUM> of a tray <NUM> and overhangs, the unstiffened wet extrudate material <NUM> exhibits an increasing degree of droop where the first end <NUM> of the wet extrudate material <NUM> is vertically displaced downwardly due to gravity. In this example, the unstiffened wet extrudate material <NUM> resulted in a droop H1 of about six inches (<NUM>) for an overhang L1 of about <NUM> inches (<NUM>). Referring to <FIG>, as the stiffened wet extrudate material <NUM> travels past the end <NUM> of the tray <NUM> and overhangs, the stiffened wet extrudate material <NUM> exhibits a significantly lower degree of droop H2 than the unstiffened wet extrudate material <NUM> of <FIG>. In this example, the unstiffened wet extrudate material <NUM> was delivered at a rate of <NUM> in/s (<NUM>/s) and treated with <NUM> KW of infrared energy centered at <NUM> microns wavelength. The stiffened wet extrudate material <NUM> had a droop H2 of less than <NUM> inches (<NUM>) for an overhang L2 of about <NUM> inches (<NUM>).

<FIG> is a chart <NUM> illustrating infrared absorption bands of wet extrudate materials <NUM> formed from the extrusion system <NUM> of <FIG>. The infrared emitting device <NUM> can be configured so that emission properties of the infrared emitting device <NUM> better match absorption of the wet extrudate material <NUM>, thereby ensuring effective coupling and lower power utilization. The chart <NUM> illustrates absorption bands in the infrared range for Composition <NUM> (including precursor material for ceramic substrate and filter products, with graphite) wet extrudate materials and Composition <NUM> (including precursor material for ceramic substrate and filter products without graphite). Similar absorption bands are present for both materials at <NUM>, <NUM>, <NUM>, and <NUM> regions. The band near <NUM> is due to OH bonds in the wet extrudate material <NUM>. The band near <NUM> is due to H<NUM>O in the wet extrudate material <NUM>. The band near <NUM> is due to inorganic oxides in the wet extrudate material <NUM>. The delivered energy increases the temperature on the skin of the wet extrudate material <NUM> leading to gelation of polymers (e.g., Methocel™), vaporization of water, and drying of skin, leading to increase in modulus and strength. As illustrated, there is wavelength sensitivity to energy coupling. Coupling with the band near <NUM> may be better suited to control depth penetration (e.g., compared to coupling with the band near <NUM>), because the peak is smaller and does not absorb as well, so that radiation impinged on wet ceramic material may penetrate more deeply.

The infrared emitting device <NUM> is configured to generate a peak emission wavelength based on a peak absorption wavelength, corresponding to infrared absorption of the wet extrudate material <NUM>. The peak absorption wavelength of a particular wet extrudate material <NUM> may be determined by optical property measurements of the wet extrudate material <NUM>. In certain embodiments, the at least one infrared emitting device <NUM> is configured to produce infrared emissions having at least one peak emission wavelength (e.g., <NUM>, <NUM>, etc.) and at least one full-width, half-maximum emission wavelength range. The wet extrudate material <NUM> includes a plurality of constituents each having an absorption spectrum having at least one peak absorption wavelength (e.g., <NUM>, <NUM>, <NUM>, etc.) and at least one full-width, half-maximum absorption wavelength range. The at least one full-width, half-maximum emission wavelength range includes at least one wavelength value within <NUM> micrometer of a wavelength of the at least one full-width, half-maximum absorption wavelength range of the absorption spectrum of at least one constituent of the plurality of constituents.

For reference, and as an example, line <NUM> around <NUM> corresponds to a CO<NUM> laser. As an example, a <NUM> W CO<NUM> laser beam rastered across a <NUM> line could be used to stiffen a <NUM> wide strip on the surface of a rectangular <NUM> thick, wet sheet of EX27 material fed at a speed of <NUM> in/s (<NUM>/s). Since CO<NUM> laser energy is absorbed by inorganic oxides, energy will be absorbed even after the wet extrudate material is dried. In certain embodiments, higher power levels may lead to heating of dried material and burning the binder. Similarly, as another example, a <NUM> diode laser with <NUM> W of power concentrated to a <NUM> spot could stiffen a <NUM> wide strip fed at <NUM> in/s (<NUM>/s) to a similar degree achievable with CO<NUM> laser treatment, but would be significantly less effective due to less efficient wavelength absorption.

In certain embodiments, CO<NUM> laser delivery may benefit from using space optics (e.g., mirrors), which may be challenging to design for uniform delivery. In certain embodiments, NIR (near infrared) lasers (e.g., diode lasers at <NUM>) could be delivered by optical fibers, but may be less effective in coupling. In one embodiment, these optical fibers could be attached to a circular ring and designed to supply energy in a near-uniform fashion on the outside surface of the wet extrudate material to achieve a zero (or near-zero) circumferential intensity gradient in intensity and high axial intensity gradient. While narrow-wavelength-band sources (e.g., lasers) can be used, broadband wavelength sources (e.g., infrared lamps) may be preferred for stiffening, since there is no requirement for coherent light sources , which can be expensive. As lasers are generally more expensive, more difficult to design for uniform delivery, and the narrow band provided by lasers is not necessary, infrared lamps with a wider band may be preferred in certain embodiments.

<FIG> is a chart <NUM> illustrating power distribution as a function of wavelength for different types of blackbody emitting devices (e.g., infrared emitting devices <NUM>) for use in the extrusion system <NUM> of <FIG>. Different types of infrared emitting devices <NUM> may be chosen depending on the application. The different types of infrared emitting devices <NUM> include halogen, NIR (near infrared), short wave, fast response medium wave, carbon, and/or medium wave. In certain embodiments, the infrared emitting device is chosen based on absorption of energy delivered by the infrared emitting device <NUM> and the ease of configuration to deliver the energy in the least amount of space. For example, in certain embodiments, a medium wave infrared emitting device may be chosen because the maximum energy is centered at around <NUM>, which coincides with OH bond peak of the wet extrudate material <NUM> for better coupling. Accordingly, the medium wave infrared emitting device may provide better performance than the short wave infrared emitting device.

<FIG> is a top view of an extrusion system <NUM> including a plurality of infrared emitting devices 102A-102C. <FIG> includes elements with common reference numbers as elements in <FIG>, and thus will not be re-described. In certain embodiments, each infrared emitting device 102A-102C of the plurality of infrared emitting devices 102A-102C is configured to produce infrared emissions of a different peak emission wavelength and a different full-width, half-maximum emission wavelength range. In certain embodiments, the plurality of infrared emitting devices 102A-102C includes a second infrared emitting device 102B positioned downstream of a first infrared emitting device 102A in the direction of travel of the wet extrudate material <NUM>, as well as a third infrared emitting device 102C positioned downstream of the first infrared emitting device 102A and the second infrared emitting device 102B in a direction of travel of the wet extrudate material <NUM>. In certain embodiments, each of the plurality of infrared emitting devices 102A-102C are each arranged in a generally cylindrical shape, and configured to irradiate the wet extrudate material <NUM> with differing total radiant flux. In certain embodiments, use of multiple infrared emitting devices 102A-102C may result in better performance and/or more manufacturing options. For example, multiple infrared emitting devices 102A-102C may allow for better depth penetration control, increased energy efficient coupling, and/or softer extrusion, etc. Of course, any number of infrared emitting devices 102A-102C could be used.

<FIG> is a front view of another embodiment of an infrared emitting device <NUM> for use in the extrusion systems <NUM>, <NUM> of <FIG> and <FIG>. The infrared emitting device <NUM> includes a plurality of circumferentially positioned emitters <NUM> (e.g., infrared emitting light emitting diodes or lasers in certain embodiments) and a diffuser <NUM> concentrically positioned relative to the plurality of circumferentially positioned emitters <NUM>. The diffuser <NUM> diffuses or scatters radiation of the circumferentially positioned emitters <NUM> to increase uniformity of irradiation of the wet extrudate material <NUM> to form the stiffened wet extrudate material <NUM>. The number and spacing of the circumferentially positioned emitters <NUM> may depend on the type of emitter <NUM>, the type of diffuser <NUM>, and the irradiation uniformity required for a particular application. In such a configuration, the plurality of circumferentially positioned emitters <NUM> may include a plurality of different types of emitters to produce a plurality of infrared emissions of differing peak emission wavelengths, differing full-width, half-maximum emission wavelength ranges, and/or differing total radiant flux.

<FIG> is a front view of a laser emitting device <NUM> for use in the extrusion systems <NUM>, <NUM> of <FIG> and <FIG>. The laser emitting device <NUM> could be used for the delivery of CO<NUM> lasers, NIR lasers, etc. The laser emitting device <NUM> includes a glass body <NUM>, an outer tubular-shaped reflector <NUM>, and an inner tubular-shaped reflector <NUM> for uniformly distribution laser radiation onto the wet extrudate material <NUM>. The inner tubular-shaped reflector <NUM> has a coating profile which leaks laser radiation to the wet extrudate material <NUM>. For example, in certain embodiments the outer tubular-shaped reflector <NUM> includes a continuous coating on the glass body <NUM> to reflect all radiation (e.g., light), and the inner tubular-shaped reflector <NUM> includes a discontinuous coating (e.g., with a plurality of circumferentially placed gaps <NUM>) on the glass body <NUM>, such that a small amount of radiation (e.g., light) is transmitted toward the center. In this way, as the radiation (e.g., light) bounces throughout the glass body <NUM>, small amounts of radiation continuously leaks out, thereby achieving uniform heating of the wet extrudate material <NUM> to form the stiffened wet extrudate material <NUM>. Alternatively, in certain embodiments, a light diffusing fiber, such as Corning Fibrance® fiber, may be used to scatter laser light uniformly around the wet extrudate material <NUM> to achieve uniform heating.

In certain embodiments, a ring-shaped resistive heater may be used. By varying the current of the heater, the emission peak wavelength can be tuned to maximize heating efficiency. According to Wien's displacement law, the peak emission wavelength is given by λ=b/T, where 'b' is Wien's constant, and 'T' is the absolute temperature in Kelvin. Changing current into the heater will result in changes in heater power and thus shift the max emission wavelength. The resistive heating elements can be made, for example, of silicon carbide (SiC), iron-chromium-aluminum (FeCrAl) wire (e.g., Kanthal® resistance wire commercially available from Sandvik AB, Hallstahammar, Sweden), or other materials known in the art. Heater designs may be based on extrusion speed, skin thickness, diameter of the wet extrudate material, etc. Heating power can be increased by increasing the size of the heating element (surface emission area), and uniform heating on the extrudate exterior can be achieved using a coiled filament design or other configurations known in the art.

The lower the temperature of the filament (resistance heating filament), the longer the wavelength and the lower the blackbody radiation intensity. This will then require a longer heating zone for equivalent radiation drying of the wet extrudate material exiting the extrusion die. As an example, assuming equal filament coverage, a halogen infrared source might be <NUM> the length of an MI (mineral insulated) heater source due to fourth power blackbody radiation. Other types of heaters that could be used are disclosed herein. Alternatively, the size (surface area) of the heating element may be increased to increase heating power.

<FIG> is a flowchart <NUM> identifying steps of a method of fabricating a stiffened wet extrudate material <NUM>. According to step <NUM>, wet extrudate material <NUM> including a honeycomb cross-section <NUM> is continuously formed from an outlet <NUM> of an extrusion die <NUM>. According to step <NUM>, a perimeter of the wet extrudate material <NUM> is uniformly irradiated with infrared emissions produced by at least one infrared emitting device <NUM> having a generally cylindrical shape with a hollow interior <NUM> and positioned downstream of the outlet <NUM> to form stiffened wet extrudate material <NUM>. In certain embodiments, the at least one infrared emitting device <NUM> comprises a plurality of infrared emitting devices 102A-102C including a first infrared emitting device 102A and a second infrared emitting device 102B positioned downstream of the first infrared emitting device 102A in a direction of travel of the wet extrudate material <NUM>. The wet extrudate material <NUM> is irradiated with a first radiant flux using the first infrared emitting device 102A and irradiated with a second radiant flux using the second infrared emitting device 102B. The second radiant flux differs from the first radiant flux. According to step <NUM>, the stiffened wet extrudate material <NUM> is passed through the hollow interior <NUM> of the at least one infrared emitting device <NUM> onto an extrudate support channel <NUM>.

Claim 1:
An extrusion system (<NUM>, <NUM>) comprising:
wet extrudate material;
an extrusion die (<NUM>) comprising an outlet (<NUM>) and configured to continuously form the wet extrudate material (<NUM>) comprising a honeycomb cross-section;
at least one infrared emitting device (<NUM>) having a hollow interior (<NUM>), positioned downstream of the outlet (<NUM>) in a direction of travel of the wet extrudate material (<NUM>), arranged in a generally cylindrical shape around a perimeter of the wet extrudate material (<NUM>), and configured to uniformly irradiate the perimeter of the wet extrudate material (<NUM>) to form stiffened wet extrudate material (<NUM>); and
an extrudate support channel (<NUM>) configured to receive the stiffened wet extrudate material (<NUM>) following passage of the wet extrudate material (<NUM>) through the hollow interior (<NUM>) of the at least one infrared emitting device (<NUM>);
wherein the at least one infrared emitting device (<NUM>) is configured to produce infrared emissions having at least one peak emission wavelength and at least one full-width, half-maximum emission wavelength range;
wherein the wet extrudate material (<NUM>) comprises a plurality of constituents each having an absorption spectrum having at least one peak absorption wavelength and at least one full-width, half-maximum absorption wavelength range; and
wherein the at least one full-width, half-maximum emission wavelength range comprises at least one wavelength value within <NUM> micrometer of a wavelength of the at least one full-width, half-maximum absorption wavelength range of the absorption spectrum of at least one constituent of the plurality of constituents.