US3899302A - Catalytic converter housing - Google Patents

Abstract

Improved automotive catalytic converter capable of operating for long periods at inlet-outlet gas temperature differentials of 1,000*F or more contains a ''''floating'''' bed of particulate catalyst. An ''''anti-backfire'''' pin maintains the spacing between the bed and the inlet housing cover and prevents any deformation caused by a sudden increase in inlet gas pressure due to the presence of excess oxygen and unburned hydrocarbons downstream of the exhaust valves. The catalyst bed or chamber is defined by a pair of facing, dish-shaped members drawn from a perforated metal screen and welded to each other along circumferential radial flange portions. The welded radial flanges on the bed are free to slidably move in their common plane of contact relative to a pair of surrounding, spaced apart flanges on the housing which are welded together at points beyond the range of movement of the bed. The anti-backfire pin is centrally mounted for rocking movement relative to the housing under thermal exercising. The pin has spherically dished washers joined to its ends which are held in sliding engagement with embossed areas in the cover members which have a corresponding shape.

Description

United States Patent Wagner Aug. 12, 1975 CATALYTIC CONVERTER HOUSING [75] lnventor: Melvin H. Wagner, Bartlett, Ill. [57] ABSTRACT [73] Assignee: Universal Oil Products Com a Improved automotive catalytic converter capable of Des Plaines [IL operating for long periods at inlet-outlet gas temperature differentials of 1,000F or more contains a float- Filed: N V- 23, 1973 ing bed of particulate catalyst. An anti-backfire [21] AppL 418,646 pin maintains the spacing between the bed and the inlet housing cover and prevents any deformation caused by a sudden increase in inlet gas pressure due U-S- CI- to the presence of excess oxygen and unburned hydro- 8/ FOIN carbons downstream of the exhaust valves. The cata- Of Search F; lyst bed o chamber is defined a pai f facing 423/212, 2 3- dish-shaped members drawn from a perforated metal screen and welded to each other along circumferential References Cited radial flange portions. The welded radial flanges on UNITED STATES PATENTS the bed are free to slidably move in their common 2,828,189 3/1958 Houdry 23/288 F Plame of Contact relative to a P of Surrounding, 2,853,367 9/1958 Karol et aL... 23/288 F Spaced apart flanges 0n the housing which are Welded 3,600,142 8/1971 Fessler 23/288 F together at points beyond the range of movement of 3.6 535 10/l972 Perga 23/288 F the bed. The anti-backfire pin is centrally mounted for 3,766.536 10/1973 Hile 23/288 F X rocking movement relative to the housing under they- 3,852,041 12/1974 Moore et al 23/288 F Primary Examiner-Joseph Scovronek Assistant Examiner-Michael S. Marcus Attorney, Agent, or Firm.lames R. Hoatson, Jr.; Barry L. Clark; William H. Page, II

mal exercising. The pin has spherically dished washers joined to its ends which are held in sliding engagement with embossed areas in the cover members which have a corresponding shape.

2 Claims, 3 Drawing Figures 90 9694 .3 110 5- 3. U A h 4 --1- CATALYTIC CONVERTER HOUSING BACKGROUND OF THE INVENTION This invention relates to catalytic converters for automotive use and particularly to converters utilizing a particulate type catalyst. In such devices, the reaction which takes place between oxygen and unburned hydrocarbons and/or CO produces a large amount of heat. Where the catalyst bed is quite large compared to the volume of exhaust gases delivered to it, or where a relatively inefficient catalyst is used, the temperature differential between the outlet and inlet sides of the converter can usually be held to 500F or less. Such a relatively small temperature difference generally does not produce any significant thermal exercising of the catalytic converter housing relative to the catalyst bed mounted therein and it is possible to weld the bed and housing directly to each other without substantially reducing the expected life of the converter.

Where space requirements do not permit the use of a large catalyst bed it is of course necessary to make the bed smaller and thus use less catalyst. This can be done by using more efficient catalysts such as platinum. However, regardless of whether a more efficient catalyst is used, the mere reduction in size of the catalyst bed will cause the converter to run hotter. For example, temperature gradients of between l200-2000F are not at all uncommon in compact converters. US. Pat. No. 3,600,142 discusses various aspects of catalytic converter operation and design and is hereby incorporated by reference. The aforementioned patent is particularly concerned with problems presented by large temperature gradients and proposes reducing these problems by providing a mounting for a catalyst bed which permits the bed to slide relative to the housing. Although the provision for a sliding mounting for a bed eliminates certain of the problems created by a large temperature differential, other problems remain. For example, excess oxygen in the exhaust path can react with unburned hydrocarbons to produce backfires or explosions characterized by sudden and very large pressure pulses contacting the inlet screen and housing and tending to force these members away from each other and deform them. The conditions are often present when the engine is decelerating. In converters that operate at low temperatures it has been proposed that the bed and the housing be rigidly held together in the direction of gas flow by one or more anti-backfire pins that pass through the bed and the housing covers and are attached thereto. Such a mounting is quite satisfactory in a rigid housing operating at a low temperature gradient but would cause stresses which would probably result in converter failure ifthere was a large temperature gradient or if the catalystbed were free to move relative to the housing.

SUMMARY I converter of the present invention which incorporates a floating CataIystbedJThe floating catalyst bed consists of two symmetrical drawn screen components having a circumferential flange portion which is welded peripherally at the outer extent of the flange so as to comprise an enclosure for containment of the catalyst pellets. The catalyst bed assembly is held in the desired position within the converter body by means of an inlet cover and an outlet cover having flanged portions configured in such manner that the catalyst bed assembly can be placed within the inlet and outlet cover so that the flanged portion of the catalyst bed assembly rests upon the lower cover flange portion, and the inlet cover flanged portion can be placed upon the opposite side of the catalyst bed flanged portion. The inlet cover is additionally flanged in such a manner that the outer periphery of the flanged portion is formed downwardly for a distance equal to the thickness of the two flanges which extend from the catalyst bed assembly. The flanges permit the inlet and outlet cover members to be attached to each other by a conventional welded process with a circumferential weld joining the flanged portion of the outlet cover and the flanged portion of the inlet cover but leaving the flanged portion of the catalyst bed assembly free to move. The downwardly formed flange portion in the inlet cover is formed with a sufficient internal diameter to allow for radial thermal exercising of the catalyst bed. As a point of illustration, one can readily appreciate that if the catalyst bed were securely welded to the inlet and outlet body cover portions of the converter, and if the body cover portions of the converter were at a lower temperature than the components comprising the catalyst bed, the body covers would act as a restraint to thermal expansion of the catalyst bed components and would cause buckling or some form of deformation as a result of the differential of temperature.

The converter assembly also includes an antibackfire pin. This pin is of such construction that when used in cooperation with a series of washers or spacers it provides a uniform desired spacing of the catalyst bed screen components and the inlet and outlet cover components and secures them together. The pin also provides resistance to the pressures of backfires in the exhaust path under all conditions of differential thermal growth between the internal screen components and the external cover components/The differential thermal growth is accommodated by providing a large pin receiving opening in the catalyst bed screen components. A pair of shouldered portions on each end of the anti-backfire pin support a pair of large circular washers which are axially spaced from each other by the thickness of the screen. The washers contact the inside portion of the screen component and the outside portion of the screen component and permit radial relative movement of the screen while sealing against passage of gases around the clearance hole in the screen. The ends of the anti-backfire pin extend outwardly from the bed assembly through an appropriate hole in the inlet and outlet cover. The areas immediately surrounding the holes in the inlet and outlet covers are spherically embossed inwardly in such manner as to accept formed washers of a complementary curved shape. The ends of the anti-backfire pin extend outwardly beyond the outward surface of each curved washer a sufficient distance to permit the pin to be welded to an additional washer which bears against the outward curved surface of the formed washers. This mounting method allows a small amount of rotational or rocking movement of the pin about any transverse axis through its center to accommodate differential thermal growth between the inlet cover portion and the outlet cover portion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view taken on line 11 of FIG. 2;

FIG. 2 is a top plan view of the improved catalytic converter with portions broken away for clarity; and

FIG. 3 is a fragmentary cross-sectional view taken on line 33 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the improved catalytic converter indicated generally at includes an inlet cover 12 and an outlet cover 14. An additional cover 16 forms a heat shield on the upper side of the converter to protect portions of the vehicle positioned above it. Engine exhaust gases are directed to the converter by an inlet tube 18 and inlet transition member 20 which are welded to the inlet cover 12. Similarly, an outlet tube 22 and outlet transition member 24 are welded to the outlet cover 14.

Positioned between the inlet and outlet covers 12, 14 is a catalyst bed assembly indicated generally at 28 and including a perforated inlet screen member 30 and a perforated outlet screen member 32. The catalyst bed assembly 28 is filled with catalyst pellets 34 through a loading tube 36 which is welded at 38 to screens 30, 32. The loading tube is also welded at 40 to cover members l2, l4 and at 42 to the heat shield 16. The loading tube 36 is closed by means of a closure plug 44.

To lend additional strength to the screen members 30, 32 the screens are embossed with ribs 48, respectively. The peripheral edges of the screen members 30,- 32 are provided with flanges 52, 54 respectively which are welded together at their peripheries by weld bead 56. The screen flanges 52, 54 are adapted for radial movement between upper cover radial flange portion 58 and lower cover radial flange portion 60 in response to differential temperature gradients between the covers and the bed assembly 28. The radial flanges 58, 60 are held in a predetermined spacing relative to each other by means of an axial flange 62 formed on the upper cover and a weld bead 64 which attaches it to flange 60. The axial flange 62 has a greater internal diameter than the external diameter of the bed assembly 28 so as to provide a space 66 for expansion of the bed assembly 28. Since the bed assembly covers l2, l4 and heat shield 16 are all welded to the loading tube 36, it is obvious that no relative movement can take place between the bed assembly 28 and the covers 12, 14 in the vicinity of the loading tube 36. Rather, movement takes place away from tube 36.

Although the aforementioned mounting of the bed assembly 28 within the cover members 12, 14 permits the bed to move freely relative to the covers in response to temperature differentials it has been found that additional structure is desirable to support the covers 12, 14 and the screens 30, 32 in the center of the converter. For this purpose, an anti-backfire pin assembly 70 is provided. The assembly 70 comprises a pin 72 having an inner shoulder 74 which bears on an inner screen retaining washer 76. The inlet screen 30 rests on the retaining washer 76 and is spaced from the pin 72 by a space 78 which accommodates thermal expansion of the screen. The pin 72 further includes an intermediate shoulder portion 80 upon which an outer screen retaining washer member 82 is positioned. The washers 76 and 82 provide some strength to the screen 30 in the vicinity of the space 78 while providing a guide for sliding movement. The pin 72 is further reduced in diameter along end portion 84 which is surrounded by flat spacer washers 86. A concave, spherically curved portion 88 of the cover member 12, having an aperture 90 larger than the diameter of the end portion 84 of the pin 72, is pressed down against the stack of washers 86 by a spherically curved washer 92 which is in turn held by a flat washer 94 and a weld bead 96.

Although only the upper end of the pin assembly 70 has been described it will be appreciated that the lower end is identical. Furthermore, while the converter 10 has been shown as having a generally circular configuration and right angled embossed ribs 48 for strengthening it will be appreciated that other shapes such as an oblong shape could be used and that the embossed ribs could be formed in other ways depending upon the strength required. For example, on an oblong shaped converter the ribs would preferably be arranged parallel to the longitudinal direction of the converter. Although a converter having 1 pin assembly 70 has been shown it will be appreciated that for larger converters strength requirements might dictate the presence of 2, 4 or more pin assemblies.

In operation, engine exhaust gases passing into the converter 10 through inlet tube 18 normally pass down through the catalyst 34 and out the outlet tube 22. In doing so they increase in temperature depending upon the amount of combustibles present so that the converter outlet screen 32 could be at a temperature of ]500F or higher as compared to an inlet temperature of perhaps 550F at the inlet cover 12. In order that the converter 10 will last for a long time, preferably 50,000 miles or more, it is constructed of material such as Type 409 stainless steel which will provide the necessary corrosion resistance and high temperature durability. Although differential temperature expansions during use of the converter are relatively small in magnitude, they are of great significance since the converter temperature is constantly rising and falling as the engine speed and load changes. Due to the presence of the spherically curved cover embossment 88 and the similarly curved washer 92 it is possible for the outlet covers 12, 14 to slide relative to the pin 72. The sliding movement prevents the pin from flexing the covers as would happen if it were welded.

I claim as my invention:

1. A catalytic converter assembly comprising a metal housing including a inlet housing cover portion and a metal outlet housing cover portion; a particulate catalyst retaining bed portion including a chamber defined by a pair of facing, dished, perforated metal inlet and outlet members; said pair of dished members having peripheral, joined together, radially extending flange portions; each of said cover portions having peripheral flanges which extend radially beyond, and slidably engage, the flange portions on said dished members; at least one of said cover portions having an axially extending flange portion which is welded to the other cover portion at a location spaced radially outwardly of the flange portions of said dished members; said bed portion being free to 'slideinthe plane of said flange portions in response to temperature differences between the metal housing and the bed portion; at least each other, a portion of said retaining means being shaped in a manner complementary to said concave shaped cover area so as to permit said retaining means to slide relative to said cover portion and said pin to pivot.

2. A catalytic converter assembly in accordance with claim 1 characterized in that a fitting for adding or removing catalyst particles passes through and is joined to said metal housing and bed portion.

Claims (2)

1. A CATALYTIC CONVERTER ASSEMBLY COMPRISING A METAL HOUSING INCLUDING A INLET HOUSING COVER PORTION AND A METAL OUTLET HOUSING COVER PORTION A PARTICULATE CATALYST RETAINING BED PORTION INCLUDING A CHAMBER DEFINED BY A PAIR OF FACING, DISHED, PERFORATED METAL INLET AND OUTLET MEMBERS, SAID PAIR OF DISHED MEMBERS HAVING PERIPHERAL, JOINED TOGETHER, RADIALLY EXTENDING FLANGE PORTIONS, EACH OF SAID COVER PORTIONS HAVING PERIPHERAL FLANGES WHICH EXTEND RADIALLY BEYOND, AND SLIDABLY ENGAGE, THE FLANGE PORTIONS ON SAID DISHED MEMBERS, AT LEAST ONE OF SAID COVER PORTIONS HAVING AN AZIALLY EXTENDING FLANGE PORTION WHICH IS WELDED TO THE OTHER COVER PORTION AT A LOCATION SPACED RADIALLY OUTWARDLY OF THE FLANGE PORTIONS OF SAID DISHED MEMBERS, SAID BED PORTION BEING FREE TO SLIDE IN THE PLANE OF SAID FLANGE PORTIONS IN RESPONSE TO TEMPERATURE DIFFERENCE BETWEEN THE METAL HOUSING AND THE BED PORTION, AT LEAST ONE SPACER PIN PASSING THROUGH SAID HOUSING COVER PORTIONS AND SAID PERFORATED MEMBERS, SAID SPACER PIN HAVING SHOULDER

2. A catalytic converter assembly in accordance with claim 1 characterized in that a fitting for adding or removing catalyst particles passes through and is joined to said metal housing and bed portion.

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