Note: Descriptions are shown in the official language in which they were submitted.
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Catalytic Converter with One Piece ~ousing
This invention relates to catalytic converters useful in m~tor
vehicle exhaust gas systems and, in particular, to converters of the
type having one or more ceramic monoliths or substrates mounted inside
of a sheet metal housing, the substrates containing a multiplicity of
longitudinal straight-through-flow exhaust gas passages that are coated
with catalyst.
.
Typically, the metal housings for commercially acceptable
converters of the type just described are of the so-called "pancake" or
"clamshell" design; i.e., they comprise stamped upper and lo~er shells,
which are substantially identical to each other, and which have mating,
peripheral, side flanges that are welded together to .lie in a plane
containing the longitudinal axis of the housing. They are shaped to
form an internal chamber in which the substrates are mounted. Another
commercial form of catalytic converter housing comprises a tube with
separate end cones welded at each end; i.e., a three-piece housing.
It is the purpose of the present invention to provide a converter
of the type described above, and the method of making it, which has a
one-piece, metal, tubular housing instead of a tw~-piece "clamshell"
housing or the three-piece end cone type housing. A converter according
to the invention performs at least as well as one having a prior type
housing but has a construction that is inherently more economical to
produce and one that can be mass-manufactured in the large volumes
required to supply original equipment converters directly to
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manufacturers of automobiles and trucks for factory installation in
exhaust systems.
The present invention involves the use of an open-ended metal tube
that has a first annular indentation formed in it to serve as a locating
and holding rib. The catalyst coated ceramic substrate with a
circumferential support mat is placed inside of the tube so that the
innermost end edge of the support mat abuts the first annular rib.
Thereafter, a second annular indentation is formed in the metal tube at
a location in which it abuts the other or outermost end edge of the
support mat so that it also serves as a locating and holding rib for the
substrate. After the substrate is positioned in thé tube, the open ends
of the tube are pinched together by radial deormation to close the ends
of the tube and form an inlet aperture in one end and an outlet aperture
in the other end. In a preferred embodiment, the above procedure is
used to position two substrates in the housinq, one being coated with
three way catalysts to convert nitrous oxides, carbon monoxide, and
hydrocarbons and the other beinq coated with oxidation catalysts to
convert carbon monoxide and hydrocarbons.
Other features and advantages of the invention will appear in the
detailed description.
Description of the Drawings
Fiqure 1 is a perspective view of a catalytic converter according
to the invention;
Figure 2 is an end view of a round tube from which the housing of
Figure 1 may be fabricated;
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Figure 3 is an enlarged section along the line 3-3 of Figure 2
sho~ing that the tube is of uniform diameter and thickness and has
smooth walls;
Figure 4 is an end view of the tube of Figure 1 after it has been
shaped into an oval with ribs.
Figure 5 is an enlarged section along the line 5-5 of Figure 4;
Figure 6 is a view similar to Figure 5 but shows two catalyst
coated substrates wrapped with support mats inserted into the tube to
seat against the ribs;
Figure 7 is a view similar to Fi~lre 6 but shows the second set of
ribs holding the substrates in place; and
Figure 8 is a view similar to Figure 7 (and corresponds to a
section along plane 8-8 of Figure 1) and shows the sec~nd set of ribs
along with the pinched down ends of the tu~e from which the converter
housing is formed.
Detailed Description of a Preferred Embodiment
In accordance with the invention, a catalytic converter 1 has a one
piece, tubular metal housing 3 with an inlet 5 at one end and an outlet
7 at the other end. A first substrate 9 with circumferentially
surrounding and narrower band-like support mat 11 is positioned inside
of the housing 3 adjacent the inlet 5 end of the housing. A second
substrate 13 with its circumferentially surrounding and narrower
band-like support mat 15 is positioned inside of the housing 3 adjacent
the outlet 7 end of the housing and is longitudinally separated from
substrate 9. The substrates 9 and 13 are of the same but smaller cross
section as the housing 3 and their outer peripheral surfaces are
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uniformly spaced radially in~ardly from tlle inner wall of the housing.
The ends of the support mats are located inwardly of the end faces of
the substrates as shown in the drawings. The support mats are composed
of a gas imyervious, vermiculite based material, available on the open
market, which is intumescent and expands substantially upon heating.
The substrates 9 and 13 subdivide the space inside of the housing 3
into three chambers; i.e., an inlet chamber 17 bet~een the inlet 5 and
the inlet side of the substrate 9, a central chamber 19 between the
outlet side of substrate 9 and the inlet side of substrate 13, and an
outlet chamber 21 between the outlet side of substrate 13 and the outlet
7. Though not illustrated, it is to be understood that each substrate
has a great number of longitudinally extending straight-through flow gas
passages and that these are coated with appropriate ea~a~ysts. Thus,
gas can flow straight through the converter 1 from inlet passage 5 to
outlet passage 7, being treated as it flows through the longitudinal
passages in the catalyst elements defined by substrates 9 and 13. The
substrate 9 may contain three-way catalysts to convert nitrous oxides,
carbon n~noxide, and hydrocarbons to nitrogen, ~ater, and carbon
dioxide. The substrate 13 may contain an oxidation catalyst and
secondary air may be supplied to chamber 19 to convert carbon m~noxide
and hydrocarbons to water and carbon dioxide. A secondary air inlet and
conduit l9A is illustrated diagrammatically in Fi~ure 8.
In further accord with the invention, a substrate locating and
holdiny means is provided in the form of a first and inner set of
annular, rib-forming indentations 23 and 25 in the wall of the tubular
housing 3 located adjacent opposite ends of central chamber 19. A
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second and outer set of similar annular rib-forming indentations 27 and
29 is also formed in housing 3 to cooperate, respectively, with ribs 23
and 25 in locating and holding the substrates 11 and 13, respectively,
in place in the housing.
Preferably, the depth of the indentations is about half the
thickness of the mats 11 and 15. This enables them to protect the ends
of the non-metallic support mats to some degree from gas flowing in the
converter and still allows some relative movement of the substrate with
respect to the housing (due to resiliency in the mats) without contact
with the substrate. The indentation 27 is spaced from the indentation
23 by a longitudinal distance that is about the same as or slightly less
than the width of the mat 11 at the time of its insertion into the
housing 3. The indentation 29 is longitudinally ~sp~ced from hte
indentation 25 by a distance that is about the same as or slightly less
than the width of the mat 15 at the time of its insertion into the
housing 3.
As seen in Figures 1 and 8, at each end of the housing opposite
sides are in engagement to close the ends of the housing. At the inlet
end, the top and bottom of the tubular housing 3 are radially deformed
or squeezed together to produce the inlet passage 5 and the
pinched-together corners 31 and 33 on opposite sides of the passage 5.
The pinched corners 31 and 35 comprise a double thickness of metal and
the two layers are preferably welded together to form and serve as
closure means that seals the inlet end of the housing except for the
formed passage 5. Similarly, at the outlet end the top and bottom of
the tubular housing 3 are radially deformed to produce the outlet
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passage 7 and the pinched-together corners 35 and 37 on opposite sides
of the passage 7. The two metal layers of the corners 35 and 37 are
preferably welded together whereby they serve as closure means to seal
the outlet end, of the housing except for the passage 7. Pinched-in end
closures of this general type in exhaust gas mufflers are shown and
described in U.S. patent 3,648,803 of March 14, 1972 of Robert A. Heath
and Ronald J. Martoia owned by the assignee of the present invention.
In general, a converter embodying the invention may be of round
cross section such as shown in Figure 1 or of other cross sections, such
as oval. The oval cross section illustrated herein is ordinarily
preferred for automotive exhaust systems because the converter can be
shaped to occupy minimum vertical space beneath the vehicle. In making
the converter 1 of this invention it is convenient ~ start with
commercially available round metal tubing and radially compress it from
opposite sides to form the oval shape of Figure 4. Preferably, this is
done by means of dies ~hich simultaneously form the annular indentations
23 and 25 to produce the shape shown in Fkgure 5. The substrates 9 and
13 with their peripheral support mats 11 and 15 are of the same outer
oval size as the inside of the ovalized housing 3 and they are stuffed
into the opposite open ends of the housing until the inner end of mat 11
is pressed against indentation 23 and the inner end of mat 15 is pressed
against indentation 25 as shown in Figure 6.
The next steps are to form the annular indentations 27 and 29 and
the inlet end closure 45 (comprising corners 31 and 33 and inlet passage
5) and the outlet end closure 47 (comprising corners 35 and 37 and
outlet passage 7~. While the indentations 27 and 29 can be rolled into
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the housing 3 before the end closures are formed, as shown in Figure 7,
it is possible to simultaneously press-form the indentations 27 and/or
29 and the end closures. This eliminates one operation and also helps
to protect the adjacent ends of the frangible substrates 9 and 13 from
damage during crimping of the end closures. It appears that the ribs on
the punch (not shown) for simultaneously pressing the indentations 23
and/or 25 and the end closures (or other parts of such punch) furnish
radial support to the ends of the housing adjacent the substrate during
pinch down of the housing ends and take some of the load to help avoid
crushing of the adjacent corners of the substrate.
The indentations 27 and 29 can be rolled in together or separately.
Alternatively, the indentations 27 and 29 to~ether with respective end
closures 45 and 47 can be formed one end at a ,,~irne or both
simultaneously. Since the converter is symmetrical, the same tooling
can be used to form one end at a time; it being necessary only to simply
reverse the housing end for end to perform the desired operation.
The engagement of each combined substrate and mat with the housing
is such as to permit them to be longitudinally stuffed into the housing
3. When used in an exhaust system the mats 11 and 15 are heated and
expand to such a degree that they tightly hold the substrates in place
without the need for mechanical assistance, ribs, or partitions.
Ordinarily, the peripheral outer surface of the substrates that engages
the mat is rough so that the mat does not tend to slip longitudinally
along the substrate even before heat expansion radially compresses it
against the outer substrate surface. However, the inner wall of housing
3 is smooth and there is a possibility of slippage between the outer
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surface of the mat and the housing until heat is applied to and the mat
expands. The pre-heat condition exists during the period between
manufacture and actual use on a vehicle. During this period much
handling of the converter occurs. Slippage at the interface between the
mat and housing is avoided, however, by the holding means provided by
rib sets 23, 27 and 25, 29. During actual use of the converter, these
indentations or ribs reduce the end areas of the mats that are exposed
to flowing gas and therefore tend to protect the mats from erosion. At
the same time they are located radially outwardly of the substrates so
that the full cross sectional areas of the substrates are available for
gas flow and treatment. Ribs have been used heretofore in converters
with "clamshell" housings in conjunction with metal mesh type substrate
supports to help hold the supports in place during a~ct~l use of the
converter. In this invention, radial compression in the support mats as
a result of heat expansion holds them in place during actual use of the
converter.
The converter illustrated contains two separate catalyst elements.
One of the elements could be omitted along with the appropriate pair of
locating and holding ribs so that the converter would contain just one
catalyst member but still embody the one piece housinc3 and rib
construction described herein.
While the converter is shown as symmetrical about a longitudinal
axis through the center lines of passages 5 and 7, it will be recognized
tllat the structure and method described would also enable one or both
passages to be transversely offset from the longitudinal axis. If
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desired, a known type of heat shield may be attached to the converter
housing 3 by welding or otherwise.
Modifications may be made in the specific features shown and
described without departing from the spirit and scope of the invention.
