CA2049634A1 - Electrically heated catalytic converter - Google Patents
Electrically heated catalytic converterInfo
- Publication number
- CA2049634A1 CA2049634A1 CA002049634A CA2049634A CA2049634A1 CA 2049634 A1 CA2049634 A1 CA 2049634A1 CA 002049634 A CA002049634 A CA 002049634A CA 2049634 A CA2049634 A CA 2049634A CA 2049634 A1 CA2049634 A1 CA 2049634A1
- Authority
- CA
- Canada
- Prior art keywords
- foil
- monolith
- catalytic converter
- catalyst support
- metal foil
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 230000003197 catalytic effect Effects 0.000 title claims abstract description 28
- 239000011888 foil Substances 0.000 claims abstract description 92
- 229910052751 metal Inorganic materials 0.000 claims abstract description 31
- 239000002184 metal Substances 0.000 claims abstract description 31
- 239000003054 catalyst Substances 0.000 claims abstract description 29
- 238000002485 combustion reaction Methods 0.000 claims abstract description 9
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 20
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 8
- 239000000919 ceramic Substances 0.000 claims description 4
- 238000010292 electrical insulation Methods 0.000 claims description 3
- 238000000576 coating method Methods 0.000 abstract description 8
- 239000011248 coating agent Substances 0.000 abstract description 6
- 239000011449 brick Substances 0.000 abstract description 2
- 239000000758 substrate Substances 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 34
- 239000007789 gas Substances 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 238000009413 insulation Methods 0.000 description 4
- 239000003344 environmental pollutant Substances 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229910000510 noble metal Inorganic materials 0.000 description 3
- 231100000719 pollutant Toxicity 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910002060 Fe-Cr-Al alloy Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 238000005219 brazing Methods 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 229910002090 carbon oxide Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 230000013011 mating Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 150000004682 monohydrates Chemical class 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 238000004901 spalling Methods 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
- F01N3/2013—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using electric or magnetic heating means
- F01N3/2026—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating using electric or magnetic heating means directly electrifying the catalyst substrate, i.e. heating the electrically conductive catalyst substrate by joule effect
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/33—Electric or magnetic properties
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
- F01N3/28—Construction of catalytic reactors
- F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
- F01N3/2807—Metal other than sintered metal
- F01N3/281—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates
- F01N3/2814—Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates all sheets, plates or foils being corrugated
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2330/00—Structure of catalyst support or particle filter
- F01N2330/02—Metallic plates or honeycombs, e.g. superposed or rolled-up corrugated or otherwise deformed sheet metal
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Catalysts (AREA)
- Exhaust Gas After Treatment (AREA)
Abstract
ELECTRICALLY HEATED CATALYTIC CONVERTER
ABSTRACT OF THE DISCLOSURE
An electrically heated catalytic converter for use in purifying the exhaust gas of an internal combustion engine has a metal foil catalyst substrate constructed of a corrugated foil strip which is continuously folded back on itself to form a monolith brick. The foil strip is coated with an electrically insulative coating to prevent shorting between adjacent layers of the monolith thereby allowing the resistance of the monolith to be tailored to allow the use of a voltage source exceeding the 12 volts typically used in automotive vehicle electrical systems.
ABSTRACT OF THE DISCLOSURE
An electrically heated catalytic converter for use in purifying the exhaust gas of an internal combustion engine has a metal foil catalyst substrate constructed of a corrugated foil strip which is continuously folded back on itself to form a monolith brick. The foil strip is coated with an electrically insulative coating to prevent shorting between adjacent layers of the monolith thereby allowing the resistance of the monolith to be tailored to allow the use of a voltage source exceeding the 12 volts typically used in automotive vehicle electrical systems.
Description
~. '? ~ "~
ELECTRICALLY HEATED CATALYTIC CONVERTER
BACRGROUND OF THE INVENTION
Field of the Invention The invention relates to electrically heated catalytic converters for use in purifying the exhaust gas of internal combustion engines and, more particularly, to a converter with an electrically heated metal foil monolith having predetermined electrical properties.
Description of the Relevant Art Typical automotive vehicle exhaust systems incorporate catalytic converters and other exhaust emis6ion control systems to assist in purifying the exhaust gas pas61ng therethrough. A catalytic converter is a device which has a catalyst dispersed on the surface of a support structure through which the ~ -exhaust gas flows. As the exhaust gas passes over the cataly6t, the pollutants unburned hydrocarbons, carbon monoxide and oxides of nitrogen are reacted to form carbon dioxide, water vapor and nitrogen. For these reactions to occur, the exhaust must be held at the proper chemical composition, and the catalyst must be at a sufficiently high temperature. During warm-up after a cold start, pollutants flow through the converter unreacted until the catalyst warms up to the light-off temperature at which reactions become significant. The efficiency of the catalyst then continue~ to increase until the converter reaches its fully warmed up operating temperature.
! .' ' . ' ' . ~ X
To decrease the amount of pollutants emitted from the tailpipe during the warm-up period, various schemes have been proposed to raise the converter temperature more quickly. These include moving the converter closer to the engine, insulating the exhaust sy6tem between the engine and the converter, reducing the thermal mas6 of the exhaust system between the engine and the converter, and electrically heating the converter. U.S. Patent No. 3,770,389 to Kitzner et al.
10 discloses an electrically heated converter constructed ;
from plate-fin corrugated metal foil which is coated with alumina and wound into a spiral. ~he coating provides insulation between the adjacent foil layers and carries the noble metals used as the catalyst. The foil is heated by a voltage applied across its length.
The Kitzner reference fails, however, to disclose a way of obtalning an adherent, insulating alumina coating on the smooth metal foil surface. Such a coating is critical to prevent electrical shorting between the foil layers. Second, tests have shown wound converters to fail by unwinding and extrusion of the foil layers, causing durability concerns. Methods used to prevent unwinding 6uch as brazing or mechanical pinning of the foil cannot be used since they result in metal-to-metal contact between the foil layers. Third, wound converters are limited to either circular or oval cross sections, and fourth, the plate-fin construction where the adjacent foil layers are in line contact increases the chances for shorting and also increases the thermal mass of the device which results in a longer time to light-off. The Kitzner patent does not contemplate the use of a power source at a voltage other than typical 12 volt automotive.
. .
", , , , ~ .
. ' .
Other electrically heated converters use the spiral wound configuration described above without insulation between the foil layers. These device6 use the 12 volt electrical 6ystem of the automobile, but with a current in the range of 500 to 600 amperes, to achieve the desired heating power. Such current ratings are undesirable from the standpoint of effect on battery life. Additionally, such low voltage, high current systems are undesirable from an efficiency ~tandpoint since a significant portion of the system resistance and power dissipation occurs in the conductors.
SUMMARY O F TH E I NVENT I ON
In accordance with the present invention, an electrically heated catalytic converter for use in purifying the exhaust gas of an internal combustion engine is di6closed. The converter comprises a metal foil catalyst substrate constructed of a corrugated Fe-Cr-~l alloy foil strip. The preferred corrugation is an alternating chevron, or herringbone pattern which allows the foil strip to be continuously folded back on itself to form a monolith brick without the problem of the adjacent layers nesting within one another.
Additionally, the herringbone corrugation is used because it reduces the possibility of electrical shorting between foil layers since contact between adjacent layers is limited to point-to-point contact rather than the line contact which occurs when the conventional plate-fin construction is used. Also, for a given frontal area, the herringbone corrugation requires less foil than a similarly performing plate-fin corrugation and, thus, reduces thermal ~ass.
The resistance of the foil monolith is tiailored to match the voltage and power available from the power supply thereby achieving maximum heating eficiency. Such re6istance tailoring iB a function of the resi~tivity of the foil, and the dimensions of the foil which must take into account the geometry of the herringbone corrugation pattern. ~ecause the resistance of the monolith can be tailored for a given power source, the use of a high voltage, low current system is contemplated. Such a power supply eliminates several problems inherent in using the 12 volt power supply of the automobile battery which requires the use of current on the order of 500 to 600 amperes.
The foil strip is coated with an insulating layer to electrically insulate adjacent foil layers when folded. The metal foil strip has an aluminum oxide layer covering substantially the entire surface thereof. Although several oxide la~er morphologies may perform satisFactorily (e.g. nodules, rosettes or blades), a layer having high a6pect ratio whiskers is preferred. Over the aluminum oxide whiskers is applied a heat resistant, electrically insulative layer. The layer comprises an alumina gel coat followed by an alumina washcoat. The aluminum oxide whiskers establish a capillary action which helps insure that the alumina gel coat solution, which is applied before the washcoat, uniformly coats and tenaciously bonds to the foil surface. The gel coat provides an excellent base for the application of the washcoat since the dried gel goes partially back into solution upon contact with the wet washcoat thereby forming an excellent bond between the coatings.
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;
Electrical leads are attached to each end of t:he foil strip and the foil monolith is wrapped in a nonconducting material (e.g. ceramlc mat) which lnsulates the monolith from its outer shell. To heat the monolith, a voltage is applied across its length.
The invention provides a heated metal monolith having a highly durable configuration which is not limited to the oval or round shapes of prior, -spiral wound foil converters. Additionally, the use of a high resistance design, which i5 resistance tailored using specific dimensional design criteria, allows the use of a high voltage, low amperage electrical source.
Other objects and features of the invention will become apparent by reference to the following `~
description and to the drawings.
BRIEF DESCRIPTION OF THE rRAWINGS
Flgure 1 is a perspective view, partially in section, of a catalytlc converter embodying the present 20 invention; -Figure 2 is a schematic view of one embodiment of the electrically heated metal foil monolith of the present invention;
Figure 3 is a partial sectional view of several layers of the electrically heated metal foil monolith of the present invention;
Figure 4 is a plan view, partially in section, of several layers of the electrically heated metal foil monolith of the present invention;
Figure 5 is a partial end view of the electrically heated metal foil monolith of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figure 1 there is shown a catalytic converter agsembly, designated generally as 10, u6ed for purifying the exhaust gas emitted from an internal combustion engine. The assembly 10 has an electrically heated catalyst support unit 12, contained in canister 14 which comprises upper and lower mating shells. The canister 14 is configured to allow the catalytic converter assembly 10 to be coupled in-line to an engine exhaust system, and is generally constructed of stainless steel or any other suitable material which is durable in an under-body exhaust environment. When installed in this manner, exhaust gas exiting the engine enters the canister 14 at inlet 16, passes through the catalyst support unit 12, where harmful exhaust constituents are converted to less harmful substances, and subsequently exits the canister at outlet 18. Although the catalytic converter assembly 10 is shown wlth a single, electrically heated catalyst support unit 12, it is contemplated that similar units with multiple catalyst supports, both heated and unheated, may be used. In such instances, the electrically heated catalyst support unit 12 is placed upstream of the unheated catalyst supports so that heating of unit 12 will assist light-off of the unheated supports. Additionally, several methods are well known for mounting such a catalyst support unit within a canister such as that represented as 14, and as such, will not be described further.
The electrically heated catalyst support unit 12 has a metal foil monolith 20 constructed of a metal foil strip 22 which is continuously folded back on itself across the frontal area of the monolith, see . . .. : i, , . . : , . . , ., .: .
Figure 2. The metal foil strip preferably comprises an Fe-Cr-Al alloy which may also contain other elements, as required, to tailor its metallurgical and electrical properti2s to predetermined applications. By varying the lengths of the respective foil layers, the monolith 20 can be formed to virtually any cross-section. The foil strip has a corrugation formed therein which iæ
configured in an alternating chevron pattern, as shown in Figures 3 and 4. The use of such a pattern prevents adjacent layers from nesting within one another as the layers are folded and, additionally, the layers contact one another in a point-to-point relationship thereby minimizing the contact area between adjacent plates and the potential for electrical shorting therebetween.
~ther corrugation patterns may also be used with similar result6. At each end of the foil monolith an electrical lead 23, 24 is attached. During operation of the converter, a voltage source (not shown) may be applied across the electrical path of the monolith 20 to heat the catalyst support, thereby reducing the time to light-off. ~ -In order to use the supplied power efficiently, the dimensions of the foil strip 22 used to construct monolith 20 are chosen so as to tailor the electrical resistance to achieve a predetermined value.
~n doing so the following equation is applied:
R - E2/Q - pL/~w where:
p - foil resistivity L - foil total length s ~
w ~ foil width - foil thickness ' and where:
L - ~(4/b + 1/a ) ]Afrontal where:
a . amplitude b - wavelength of the corrugation pattern, and A - frontal area Application of the above equations in determining the dimensions of the monolith allows the choice of a power configuration best suited to the particular application. In the present case, it i8 contemplated that a monolith reslgtance of approxlmately 2.5 ohms allows the use of a relatlvely low current, in the range of 25 to 32 amperes, and a relatively high voltage, in the range of 62 to 80 volts which will ;~
regult in a power rating at the converter of 1500 to 2500 watts which is desirable from the standpoint of safety and durability. Thi~ differs greatly fro~ the 500+ amperes which would be required in an electrically heated converter operating at the 12 volt level of the automobile with a monolith electrical resistance `on the order of millions.
In order for the foil strip 22 to present a high resistance path acro~s its length while folded in the configuration of monolith 20, electrical insulation must be provided between the adjacent layers thereof.
The insulation, illustrated in Figure 5, must be ;;
" . ., . . , . . , . . .. j . ~ . , . i . : . . . . . . . ~ . .
effective without interfering with the flow of exhaust gas through the monolith and must be highly resistant to degradation that would subject adjacent foil layers to contact and electrical shorting.
The insulative coating applied to the foil strip comprises several layers. The first, or base layer, is an aluminum oxide which covers substantially the entire foil strip. The aluminum oxide layer is oxidized on the surface of the foil strip 22 using a process similar to that described in U.S. Patent No.
4,588,499 to Sigler and in U.S. Patent No. 4,318,828 to Chapman, assigned to the assignee of the present invention and incorporated herein by reference. The oxide may take several forms; however, a high-aspect-ratio whisker is preferred. The whiskers act in a capillary manner to absorb and hold subsequent coating layers and, as a result, contribute to an overall electrlcally insulative layer which i6 hlghly reslstant to spalling and loss.
The second layer applied to the foil monolith ls an alumina gel coat 26. The gel i6 6imilar to that described in the Chapman patent and i6 made by combining typically 5 wt% alumina monohydrate with water and 5 wt% nitric acid. Several applications of the gel coat 26 may be applied to the folded, whiskered monolith in its uncompressed state (described below) to -~
assure adequate coverage of all foil layers.
The third layer applied to the foil monolith is an alumina washcoat 28. The washcoat is of the type described in the Chapman patent and may, or may not, contain noble metals. The washcoat may also take the 3 .~ ~
form of other commercially available washcoats which have characteristics which allow suitable bonding with the alumina gel coat 26.
There are various po6sibilitie6 for the application of the above de6cri~ed in6ulative layers to the monolith. It is preferable, however, to apply the alumina gel coat to the folded, uncompre6sed foil monolith 20. In other words, the gel coating is applied after the foil monolith 20 has been folded to the desired shape, but before further steps, described in detail below, are performed. The uncompressed application assures that the gel layer will uniformly coat the foil thereby providing the be6t insulation ;
between adjacent layers. Several coats of the alumina gel 26 may be applied.
Following the application of the alumina gel layer 26, the foil monolith is compressed to the size required to fit the cataly6t 6upport unit shell 30.
The shell 30, shown in Figure 1, generally comprise6 a two piece clamshell assembly which is secured around the monolith 20 and acts to rigidly restrain the monolith within canister 14. Other canister configurations, such as single piece, tubular shells with individual end cones may also be used. In order to prevent electrical shorting between the metal foil monolith 20 and the shell 30, an insulating material, such as ceramic mat 32 is wrapped about the outer periphery of the compressed foil monolith 20 prior to placement within the shell 30. The assembled monolith may receive an additional application of the alumina gel coat 26 which will penetrate the insulating material giving it strength and rigidity as well as reducing its ability to absorb noble metals which are subsequently applied. The alumina gel coat 26 provides a good base for the subsequent application of the wa8hcoat 28 since the dried gel goes partially back into solution upon contact with the wet washcoat. As a S result, a very tenacious bond between the two coatings i6 formed.
Although the description of the present invention heretofore disclosed is directed towards a single-strip foil monolith, in order to achieve greater flexibility in resistance tailoring of the metal foil monolith 20, it is contemplated that more than one foil strip 22 may be used in a single monolith 20, as shown in Figure 2. The monoliths are electrically connected in parallel in order to reduce the resistance of the lS overall catalytic converter. In the alternative, the monoliths may be electrically connected in series (not shown) in order to increase the resistance of the catalytic converter.
While certain embodiments of the invention have been described in detail above in relation to an electrically heated metal monolith catalytic converter, it would be apparent to those skilled in the art that the di6closed embodiment may be modified. Therefore, the foregoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the following claims.
ELECTRICALLY HEATED CATALYTIC CONVERTER
BACRGROUND OF THE INVENTION
Field of the Invention The invention relates to electrically heated catalytic converters for use in purifying the exhaust gas of internal combustion engines and, more particularly, to a converter with an electrically heated metal foil monolith having predetermined electrical properties.
Description of the Relevant Art Typical automotive vehicle exhaust systems incorporate catalytic converters and other exhaust emis6ion control systems to assist in purifying the exhaust gas pas61ng therethrough. A catalytic converter is a device which has a catalyst dispersed on the surface of a support structure through which the ~ -exhaust gas flows. As the exhaust gas passes over the cataly6t, the pollutants unburned hydrocarbons, carbon monoxide and oxides of nitrogen are reacted to form carbon dioxide, water vapor and nitrogen. For these reactions to occur, the exhaust must be held at the proper chemical composition, and the catalyst must be at a sufficiently high temperature. During warm-up after a cold start, pollutants flow through the converter unreacted until the catalyst warms up to the light-off temperature at which reactions become significant. The efficiency of the catalyst then continue~ to increase until the converter reaches its fully warmed up operating temperature.
! .' ' . ' ' . ~ X
To decrease the amount of pollutants emitted from the tailpipe during the warm-up period, various schemes have been proposed to raise the converter temperature more quickly. These include moving the converter closer to the engine, insulating the exhaust sy6tem between the engine and the converter, reducing the thermal mas6 of the exhaust system between the engine and the converter, and electrically heating the converter. U.S. Patent No. 3,770,389 to Kitzner et al.
10 discloses an electrically heated converter constructed ;
from plate-fin corrugated metal foil which is coated with alumina and wound into a spiral. ~he coating provides insulation between the adjacent foil layers and carries the noble metals used as the catalyst. The foil is heated by a voltage applied across its length.
The Kitzner reference fails, however, to disclose a way of obtalning an adherent, insulating alumina coating on the smooth metal foil surface. Such a coating is critical to prevent electrical shorting between the foil layers. Second, tests have shown wound converters to fail by unwinding and extrusion of the foil layers, causing durability concerns. Methods used to prevent unwinding 6uch as brazing or mechanical pinning of the foil cannot be used since they result in metal-to-metal contact between the foil layers. Third, wound converters are limited to either circular or oval cross sections, and fourth, the plate-fin construction where the adjacent foil layers are in line contact increases the chances for shorting and also increases the thermal mass of the device which results in a longer time to light-off. The Kitzner patent does not contemplate the use of a power source at a voltage other than typical 12 volt automotive.
. .
", , , , ~ .
. ' .
Other electrically heated converters use the spiral wound configuration described above without insulation between the foil layers. These device6 use the 12 volt electrical 6ystem of the automobile, but with a current in the range of 500 to 600 amperes, to achieve the desired heating power. Such current ratings are undesirable from the standpoint of effect on battery life. Additionally, such low voltage, high current systems are undesirable from an efficiency ~tandpoint since a significant portion of the system resistance and power dissipation occurs in the conductors.
SUMMARY O F TH E I NVENT I ON
In accordance with the present invention, an electrically heated catalytic converter for use in purifying the exhaust gas of an internal combustion engine is di6closed. The converter comprises a metal foil catalyst substrate constructed of a corrugated Fe-Cr-~l alloy foil strip. The preferred corrugation is an alternating chevron, or herringbone pattern which allows the foil strip to be continuously folded back on itself to form a monolith brick without the problem of the adjacent layers nesting within one another.
Additionally, the herringbone corrugation is used because it reduces the possibility of electrical shorting between foil layers since contact between adjacent layers is limited to point-to-point contact rather than the line contact which occurs when the conventional plate-fin construction is used. Also, for a given frontal area, the herringbone corrugation requires less foil than a similarly performing plate-fin corrugation and, thus, reduces thermal ~ass.
The resistance of the foil monolith is tiailored to match the voltage and power available from the power supply thereby achieving maximum heating eficiency. Such re6istance tailoring iB a function of the resi~tivity of the foil, and the dimensions of the foil which must take into account the geometry of the herringbone corrugation pattern. ~ecause the resistance of the monolith can be tailored for a given power source, the use of a high voltage, low current system is contemplated. Such a power supply eliminates several problems inherent in using the 12 volt power supply of the automobile battery which requires the use of current on the order of 500 to 600 amperes.
The foil strip is coated with an insulating layer to electrically insulate adjacent foil layers when folded. The metal foil strip has an aluminum oxide layer covering substantially the entire surface thereof. Although several oxide la~er morphologies may perform satisFactorily (e.g. nodules, rosettes or blades), a layer having high a6pect ratio whiskers is preferred. Over the aluminum oxide whiskers is applied a heat resistant, electrically insulative layer. The layer comprises an alumina gel coat followed by an alumina washcoat. The aluminum oxide whiskers establish a capillary action which helps insure that the alumina gel coat solution, which is applied before the washcoat, uniformly coats and tenaciously bonds to the foil surface. The gel coat provides an excellent base for the application of the washcoat since the dried gel goes partially back into solution upon contact with the wet washcoat thereby forming an excellent bond between the coatings.
- . . .. .
., . ~
;
Electrical leads are attached to each end of t:he foil strip and the foil monolith is wrapped in a nonconducting material (e.g. ceramlc mat) which lnsulates the monolith from its outer shell. To heat the monolith, a voltage is applied across its length.
The invention provides a heated metal monolith having a highly durable configuration which is not limited to the oval or round shapes of prior, -spiral wound foil converters. Additionally, the use of a high resistance design, which i5 resistance tailored using specific dimensional design criteria, allows the use of a high voltage, low amperage electrical source.
Other objects and features of the invention will become apparent by reference to the following `~
description and to the drawings.
BRIEF DESCRIPTION OF THE rRAWINGS
Flgure 1 is a perspective view, partially in section, of a catalytlc converter embodying the present 20 invention; -Figure 2 is a schematic view of one embodiment of the electrically heated metal foil monolith of the present invention;
Figure 3 is a partial sectional view of several layers of the electrically heated metal foil monolith of the present invention;
Figure 4 is a plan view, partially in section, of several layers of the electrically heated metal foil monolith of the present invention;
Figure 5 is a partial end view of the electrically heated metal foil monolith of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figure 1 there is shown a catalytic converter agsembly, designated generally as 10, u6ed for purifying the exhaust gas emitted from an internal combustion engine. The assembly 10 has an electrically heated catalyst support unit 12, contained in canister 14 which comprises upper and lower mating shells. The canister 14 is configured to allow the catalytic converter assembly 10 to be coupled in-line to an engine exhaust system, and is generally constructed of stainless steel or any other suitable material which is durable in an under-body exhaust environment. When installed in this manner, exhaust gas exiting the engine enters the canister 14 at inlet 16, passes through the catalyst support unit 12, where harmful exhaust constituents are converted to less harmful substances, and subsequently exits the canister at outlet 18. Although the catalytic converter assembly 10 is shown wlth a single, electrically heated catalyst support unit 12, it is contemplated that similar units with multiple catalyst supports, both heated and unheated, may be used. In such instances, the electrically heated catalyst support unit 12 is placed upstream of the unheated catalyst supports so that heating of unit 12 will assist light-off of the unheated supports. Additionally, several methods are well known for mounting such a catalyst support unit within a canister such as that represented as 14, and as such, will not be described further.
The electrically heated catalyst support unit 12 has a metal foil monolith 20 constructed of a metal foil strip 22 which is continuously folded back on itself across the frontal area of the monolith, see . . .. : i, , . . : , . . , ., .: .
Figure 2. The metal foil strip preferably comprises an Fe-Cr-Al alloy which may also contain other elements, as required, to tailor its metallurgical and electrical properti2s to predetermined applications. By varying the lengths of the respective foil layers, the monolith 20 can be formed to virtually any cross-section. The foil strip has a corrugation formed therein which iæ
configured in an alternating chevron pattern, as shown in Figures 3 and 4. The use of such a pattern prevents adjacent layers from nesting within one another as the layers are folded and, additionally, the layers contact one another in a point-to-point relationship thereby minimizing the contact area between adjacent plates and the potential for electrical shorting therebetween.
~ther corrugation patterns may also be used with similar result6. At each end of the foil monolith an electrical lead 23, 24 is attached. During operation of the converter, a voltage source (not shown) may be applied across the electrical path of the monolith 20 to heat the catalyst support, thereby reducing the time to light-off. ~ -In order to use the supplied power efficiently, the dimensions of the foil strip 22 used to construct monolith 20 are chosen so as to tailor the electrical resistance to achieve a predetermined value.
~n doing so the following equation is applied:
R - E2/Q - pL/~w where:
p - foil resistivity L - foil total length s ~
w ~ foil width - foil thickness ' and where:
L - ~(4/b + 1/a ) ]Afrontal where:
a . amplitude b - wavelength of the corrugation pattern, and A - frontal area Application of the above equations in determining the dimensions of the monolith allows the choice of a power configuration best suited to the particular application. In the present case, it i8 contemplated that a monolith reslgtance of approxlmately 2.5 ohms allows the use of a relatlvely low current, in the range of 25 to 32 amperes, and a relatively high voltage, in the range of 62 to 80 volts which will ;~
regult in a power rating at the converter of 1500 to 2500 watts which is desirable from the standpoint of safety and durability. Thi~ differs greatly fro~ the 500+ amperes which would be required in an electrically heated converter operating at the 12 volt level of the automobile with a monolith electrical resistance `on the order of millions.
In order for the foil strip 22 to present a high resistance path acro~s its length while folded in the configuration of monolith 20, electrical insulation must be provided between the adjacent layers thereof.
The insulation, illustrated in Figure 5, must be ;;
" . ., . . , . . , . . .. j . ~ . , . i . : . . . . . . . ~ . .
effective without interfering with the flow of exhaust gas through the monolith and must be highly resistant to degradation that would subject adjacent foil layers to contact and electrical shorting.
The insulative coating applied to the foil strip comprises several layers. The first, or base layer, is an aluminum oxide which covers substantially the entire foil strip. The aluminum oxide layer is oxidized on the surface of the foil strip 22 using a process similar to that described in U.S. Patent No.
4,588,499 to Sigler and in U.S. Patent No. 4,318,828 to Chapman, assigned to the assignee of the present invention and incorporated herein by reference. The oxide may take several forms; however, a high-aspect-ratio whisker is preferred. The whiskers act in a capillary manner to absorb and hold subsequent coating layers and, as a result, contribute to an overall electrlcally insulative layer which i6 hlghly reslstant to spalling and loss.
The second layer applied to the foil monolith ls an alumina gel coat 26. The gel i6 6imilar to that described in the Chapman patent and i6 made by combining typically 5 wt% alumina monohydrate with water and 5 wt% nitric acid. Several applications of the gel coat 26 may be applied to the folded, whiskered monolith in its uncompressed state (described below) to -~
assure adequate coverage of all foil layers.
The third layer applied to the foil monolith is an alumina washcoat 28. The washcoat is of the type described in the Chapman patent and may, or may not, contain noble metals. The washcoat may also take the 3 .~ ~
form of other commercially available washcoats which have characteristics which allow suitable bonding with the alumina gel coat 26.
There are various po6sibilitie6 for the application of the above de6cri~ed in6ulative layers to the monolith. It is preferable, however, to apply the alumina gel coat to the folded, uncompre6sed foil monolith 20. In other words, the gel coating is applied after the foil monolith 20 has been folded to the desired shape, but before further steps, described in detail below, are performed. The uncompressed application assures that the gel layer will uniformly coat the foil thereby providing the be6t insulation ;
between adjacent layers. Several coats of the alumina gel 26 may be applied.
Following the application of the alumina gel layer 26, the foil monolith is compressed to the size required to fit the cataly6t 6upport unit shell 30.
The shell 30, shown in Figure 1, generally comprise6 a two piece clamshell assembly which is secured around the monolith 20 and acts to rigidly restrain the monolith within canister 14. Other canister configurations, such as single piece, tubular shells with individual end cones may also be used. In order to prevent electrical shorting between the metal foil monolith 20 and the shell 30, an insulating material, such as ceramic mat 32 is wrapped about the outer periphery of the compressed foil monolith 20 prior to placement within the shell 30. The assembled monolith may receive an additional application of the alumina gel coat 26 which will penetrate the insulating material giving it strength and rigidity as well as reducing its ability to absorb noble metals which are subsequently applied. The alumina gel coat 26 provides a good base for the subsequent application of the wa8hcoat 28 since the dried gel goes partially back into solution upon contact with the wet washcoat. As a S result, a very tenacious bond between the two coatings i6 formed.
Although the description of the present invention heretofore disclosed is directed towards a single-strip foil monolith, in order to achieve greater flexibility in resistance tailoring of the metal foil monolith 20, it is contemplated that more than one foil strip 22 may be used in a single monolith 20, as shown in Figure 2. The monoliths are electrically connected in parallel in order to reduce the resistance of the lS overall catalytic converter. In the alternative, the monoliths may be electrically connected in series (not shown) in order to increase the resistance of the catalytic converter.
While certain embodiments of the invention have been described in detail above in relation to an electrically heated metal monolith catalytic converter, it would be apparent to those skilled in the art that the di6closed embodiment may be modified. Therefore, the foregoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the following claims.
Claims (14)
1. An electrically heated catalyst support for use with a catalytic converter comprising:
a metal foil monolith comprising a corrugated foil strip continuously folded back on itself across the frontal area of said monolith, an oxide layer covering substantially the entire surface of said foil strip;
a heat resistant, electrically insulative layer applied to said oxide layer to electrically insulate said adjacent foil layers and establish a high resistance, single electrical path across the length of said foil strip; and electrical leads connected to each end of said foil strip, wherein a voltage source is applied across said electrical path of said metal foil monolith to heat said catalyst support.
a metal foil monolith comprising a corrugated foil strip continuously folded back on itself across the frontal area of said monolith, an oxide layer covering substantially the entire surface of said foil strip;
a heat resistant, electrically insulative layer applied to said oxide layer to electrically insulate said adjacent foil layers and establish a high resistance, single electrical path across the length of said foil strip; and electrical leads connected to each end of said foil strip, wherein a voltage source is applied across said electrical path of said metal foil monolith to heat said catalyst support.
2. An electrically heated catalyst support for use with a catalytic converter, as defined in claim 1, said corrugation comprising an alternating chevron pattern.
3. An electrically heated catalyst support for use with a catalytic converter, as defined in claim 1, wherein the dimensions of said metal foil monolith are tailored to achieve a predetermined electrical resistance by applying the equation:
R = E2/Q = ?L/.delta.w where:
p = foil resistivity L = foil total length w = foil width .delta. = foil thickness and where:
L ~ [(4/b2 + 1/a2)?]Afrontal where:
a = amplitude b = wavelength of said corrugation pattern, and A = frontal area
R = E2/Q = ?L/.delta.w where:
p = foil resistivity L = foil total length w = foil width .delta. = foil thickness and where:
L ~ [(4/b2 + 1/a2)?]Afrontal where:
a = amplitude b = wavelength of said corrugation pattern, and A = frontal area
4. An electrically heated catalyst support for use with a catalytic converter, as defined in claim 3, wherein said electrical resistance is tailored to allow the use of a voltage source greater than 12 volts.
5. An electrically heated catalyst support for use with a catalytic converter, as defined in claim 1, wherein said oxide layer comprises a high aspect ratio aluminum oxide whisker.
6. An electrically heated catalyst support for use with a catalytic converter, as defined in claim 1, wherein said electrically insulative layer comprises:
a first alumina gel coat applied to said oxide layer; and a second alumina washcoat applied to said first alumina gel coat.
a first alumina gel coat applied to said oxide layer; and a second alumina washcoat applied to said first alumina gel coat.
7. An electrically heated catalyst support for use with a catalytic converter, as defined in claim 1, wherein said catalyst support comprises more than one metal foil strip electrically connected in parallel.
8. An electrically heated catalyst support for use with a catalytic converter, as defined in claim 1, wherein said catalyst support comprises more than one metal foil strip electrically connected in series.
9. An electrically heated catalyst support for use with a catalytic converter, as defined in claim 1, further comprising:
a ceramic mat wrapped about the exterior of said metal foil monolith; and a rigid retainer shell enclosing said metal foil monolith and ceramic mat assembly;
said ceramic mat providing electrical insulation between said metal foil monolith and said retainer shell.
a ceramic mat wrapped about the exterior of said metal foil monolith; and a rigid retainer shell enclosing said metal foil monolith and ceramic mat assembly;
said ceramic mat providing electrical insulation between said metal foil monolith and said retainer shell.
10. A catalytic converter for purifying the exhaust gas of an internal combustion engine comprising:
a metal foil monolith comprising a corrugated foil strip continuously folded back on itself across the frontal area thereof and having dimensions tailored to a predetermined electrical resistance by applying the equation:
R - E2/Q = ?L/.delta.w where:
? = foil resistivity L = foil total length w = foil width .delta. = foil thickness and where:
L ~ [(4/b2 + 1/a2)1/2]Afrontal where:
a = amplitude b = wavelength of said corrugation pattern, and A = frontal area electrical leads connected to each end of said foil strip;
an oxide layer covering substantially the entire surface of said foil strip;
a heat resistant, electrically insulative layer applied to said oxide layer to electrically insulate said adjacent foil layers and establish a high resistance, single electrical path across the length of said foil strip;
an insulative mat wrapped about the exterior of said metal foil monolith; and a rigid retainer shell enclosing said metal foil monolith and insulative mat assembly;
said insulative mat providing electrical insulation between said metal foil monolith and said retainer shell;
wherein a voltage source is applied across said electrical path of said metal foil monolith to heat said catalyst support.
a metal foil monolith comprising a corrugated foil strip continuously folded back on itself across the frontal area thereof and having dimensions tailored to a predetermined electrical resistance by applying the equation:
R - E2/Q = ?L/.delta.w where:
? = foil resistivity L = foil total length w = foil width .delta. = foil thickness and where:
L ~ [(4/b2 + 1/a2)1/2]Afrontal where:
a = amplitude b = wavelength of said corrugation pattern, and A = frontal area electrical leads connected to each end of said foil strip;
an oxide layer covering substantially the entire surface of said foil strip;
a heat resistant, electrically insulative layer applied to said oxide layer to electrically insulate said adjacent foil layers and establish a high resistance, single electrical path across the length of said foil strip;
an insulative mat wrapped about the exterior of said metal foil monolith; and a rigid retainer shell enclosing said metal foil monolith and insulative mat assembly;
said insulative mat providing electrical insulation between said metal foil monolith and said retainer shell;
wherein a voltage source is applied across said electrical path of said metal foil monolith to heat said catalyst support.
11. A catalytic converter for purifying the exhaust gas of an internal combustion engine, as defined in claim 10, wherein said oxide layer comprises a high aspect ratio aluminum oxide whisker.
12. A catalytic converter for purifying the exhaust gas of an internal combustion engine, as defined in claim 10, wherein said electrically insulative layer comprises:
a first alumina gel coat applied to said aluminum oxide layer; and a second alumina washcoat applied to said first alumina gel coat.
a first alumina gel coat applied to said aluminum oxide layer; and a second alumina washcoat applied to said first alumina gel coat.
13. A catalytic converter for purifying the exhaust gas of an internal combustion engine as defined in claim 10, wherein said voltage source is greater than 12 volts.
14. A catalytic converter for purifying the exhaust gas of an internal combustion engine as defined in claim 10, said corrugation comprising an alternating chevron pattern.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US57655690A | 1990-08-31 | 1990-08-31 | |
| US576,556 | 1990-08-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2049634A1 true CA2049634A1 (en) | 1992-03-01 |
Family
ID=24304920
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002049634A Abandoned CA2049634A1 (en) | 1990-08-31 | 1991-08-21 | Electrically heated catalytic converter |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA2049634A1 (en) |
| DE (1) | DE4128924A1 (en) |
| GB (1) | GB2247413B (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4306482C2 (en) * | 1992-03-12 | 1994-11-17 | Emitec Emissionstechnologie | Use of a ceramic plasticine to produce an insulating layer |
| US5288470A (en) * | 1992-10-02 | 1994-02-22 | W. R. Grace & Co.-Conn. | Metal substrate having an insulating barrier |
| US5393586A (en) * | 1992-10-27 | 1995-02-28 | Corning Incorporated | Localized electrical heating of honeycomb structures |
| US5519191A (en) * | 1992-10-30 | 1996-05-21 | Corning Incorporated | Fluid heater utilizing laminar heating element having conductive layer bonded to flexible ceramic foil substrate |
| DE4243904A1 (en) * | 1992-12-23 | 1994-06-30 | Roth Technik Gmbh | catalyst |
| FR2703206B1 (en) * | 1993-03-26 | 1995-07-07 | Ecia Equip Composants Ind Auto | DEVICE FOR HEATING A CATALYTIC PURIFICATION ELEMENT OF EXHAUST GASES OF AN ENGINE, PARTICULARLY A MOTOR VEHICLE. |
| DE19508376A1 (en) * | 1995-03-10 | 1996-09-12 | Roth Technik Gmbh | Electrically heated catalyst |
| US5786031A (en) * | 1995-06-07 | 1998-07-28 | Engelhard Corporation | Barrier for a metal substrate |
| US6060173A (en) * | 1996-04-17 | 2000-05-09 | Englehard Corporation | Metal honeycomb body |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3770389A (en) * | 1971-11-11 | 1973-11-06 | Ford Motor Co | Catalytic converter with electrically resistive catalyst support |
| DE8536843U1 (en) * | 1984-09-13 | 1990-01-04 | W.R. Grace & Co.-Conn., New York, N.Y. | Metal strip for producing a catalyst carrier |
| US4711009A (en) * | 1986-02-18 | 1987-12-08 | W. R. Grace & Co. | Process for making metal substrate catalytic converter cores |
| DE8816514U1 (en) * | 1988-04-25 | 1989-10-26 | Emitec Gesellschaft für Emissionstechnologie mbH, 5204 Lohmar | Electrically heated catalyst carrier body |
| DE3923094C2 (en) * | 1989-07-13 | 1993-11-25 | Ltg Lufttechnische Gmbh | Catalyst carrier body |
-
1991
- 1991-08-19 GB GB9117846A patent/GB2247413B/en not_active Expired - Fee Related
- 1991-08-21 CA CA002049634A patent/CA2049634A1/en not_active Abandoned
- 1991-08-30 DE DE4128924A patent/DE4128924A1/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| DE4128924A1 (en) | 1992-03-12 |
| GB9117846D0 (en) | 1991-10-09 |
| GB2247413B (en) | 1994-05-18 |
| GB2247413A (en) | 1992-03-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |