Catalytic converter bed support means

Abstract

A low profile catalytic converter made of sheet metal wherein catalyst material is contained in a space between top and bottom catalyst retaining plates which in turn are located between top and bottom shells to define a structure wherein engine exhaust gases entering at one end of the converter pass through the catalyst material and exit at the opposite end. Sagging of the bottom catalyst retaining plate is avoided by one or more elongated support channels each having a web in face-to-face supporting relation to the bottom shell and upstanding longitudinal sides which fit against and support the bottom catalyst retaining plate at a series of spaced points along their lengths. Each support channel includes a web that is struck upwardly to define a pair of flat portions that fit against and are welded to the bottom catalyst retaining plate, one of these flat portions has fore and aft rigidity while the other has fore and aft flexibility, so that the welds do not break under the temperature gradients and varying thermal expansion conditions of the converter, when used.

Description

This application covers an improvement over the invention covered by application U.S. Ser. No. 262,708 filed June 14, 1972 titled "Low Profile Catalytic Converter", assigned to the same assignee. More particularly, the present application relates to a construction wherein the bottom catalyst retaining plate is supported from the lower shell to prevent the plate from sagging. Such sagging can impede or cut off the exhaust flow through the converter by blocking the outlet plenum chamber and can enlarge the catalyst container with resultant rapid attrition of catalyst pellets.

The converter as used and disclosed is light enough to be supported by the exhaust system and is designed to resist deformation such as bulging of the outside members as well as bulging of the bottom catalyst retaining plate, which results from the combined effect of the weight of the pellets and the elevated operating temperatures of the converter which temperatures can rise to and above about 1600.degree.F. It is contemplated that the converter will be filled with a catalyst material formed as beads or slugs, and it is therefore a requirement that the catalyst bed be kept as tightly packed as possible during operation to prevent attrition of the catalyst generally brought about by the breaking up of the pellets from both road vibration and fluidization of the catalyst bed by the exhaust gases flowing therethrough. It is a further requirement that the flow of gases through the catalyst bed be substantially uniformly distributed throughout the bed for maximum catalyst life and optimum conversion. Additionally, the flow of gases through the outlet of the converter must not be impeded to assure maximum flow and preclude any back pressure through the exhaust system.

Accordingly, it is an object of this invention to provide a catalytic converter suitable for treatment of automobile exhaust gases meeting the aforementioned requirements.

It is a further object to provide a catalytic converter having support means on the bottom catalyst retaining plate to prevent the retaining plate from sagging thereby preventing any impedance in the flow of exhaust gases from the converter.

It is a further object to provide a catalytic converter having support means that is adapted to be easily attached to the bottom catalyst retaining plate.

It is a further object of this invention to provide a catalytic converter having support means that is channel shaped which will not impede the flow through the converter, but will provide an area of support as well as a channel through which the exhaust gas can flow.

It is a further object of the present invention to provide an improved catalyst converter wherein the bottom catalyst retaining plate is supported at a plurality of longitudinally spaced points from the bottom shell member and having features of construction, combination, and arrangement wherein the support is provided by one or more channels each welded at longitudinally spaced points to the bottom catalyst retaining plate and having one weldable portion securing the channel rigidly to the bottom catalyst retaining plate as to fore and aft movement and another weldable portion that yieldably secures the channel to the bottom catalyst retaining plate to accommodate differential expansion and contraction of the members without undue weld stress, and further wherein minimum obstruction of gas flow through the converter occurs and the heat flow from the bottom catalyst retaining plate to the bottom shell members is not substantially increased, and in other respects a unit characterized by a high degree of effectiveness, low cast and ease of manufacture is provided.

Other objects and advantages of this invention will become apparent from the following detailed description, reference being had to the accompanying drawings of which:

FIG. 1 is a side elevational view of a catalytic converter with attached exhaust inlet and outlet pipes.

FIG. 2 is a horizontal cross sectional view from the bottom of the converter on line 2--2 of FIG. 1 showing the bottom catalyst retaining plate having the support members positioned thereon.

FIG. 3 is a cross sectional view taken along line 3--3 of FIG. 2.

FIG. 4 is a cross sectional view taken along line 4--4 of FIG. 1.

FIG. 5 is an enlarged portion of FIG. 3 showing the rear channel support tab.

FIG. 6 is a view in perspective of a support channel element constructed in accordance with the present invention.

FIG. 7 is an enlarged portion of FIG. 3 showing the forward channel support tab.

FIG. 8 is a view like FIG. 2 of an alternative embodiment of the present invention.

Referring to the drawings, the catalytic converter assembly or housing 10 as shown in FIGS. 1 - 4 includes a dished top housing plate or shell 12 and a bottom dished housing plate or shell 14 having side wall portions 16 and 18, respectively, FIG. 4, with peripheral flange portions 20, 22, respectively, extending outwardly therefrom substantially about the entire periphery in mating relation to each other.

Mounted within housing 10 is an inclined catalyst retaining element 24 which includes a dished top plate 26 that has a top portion 30 located below and spaced from the top housing plate or shell 12 and having a plurality of regularly spaced perforations or louvers 32 therethrough. The louvers are formed by pierced strap-like sections of the plate 26 which are bent upwardly as shown to form side-facing openings for gas flow. Similarly, the dished bottom plate 28 includes a bottom portion 34 spaced from the bottom housing plate or shell 14 that also has a plurality of similar regularly spaced perforations or louvers 36 therethrough.

Catalyst retaining element 24 also includes gas impervious sidewall portions 38 and 40, respectively, spaced from the sidewall portions 16 and 18 of the housing 10 and having mating peripheral flange portions 42 and 44 extending therefrom. These flange portions are sandwiched between the peripheral flange portions 20 and 22 of the shells 12 and 14, as shown. Catalyst retaining plates 26 and 28 thus define a catalyst retaining space 46 of substantially uniform depth between plates 26 and 28. As seen in FIG. 3 the distance of plate 26 from the housing plate or shell 12 progressively decreases from left to right so as to form a progressively decreased cross section for incoming exhaust gas flow. Similarly, the distance between plate 28 and shell 14 progressively increases from left to right so as to provide a progressively increased cross section for outflow of the exhaust gases. The space between catalyst retaining plate 28 and shell 14 should remain as unobstructed to gas flow as possible to provide for an unimpeded outflow of exhaust gas. The means of maintaining an unobstructed space between catalyst retaining plate 28 and shell 14 under elevated operating and excursion temperatures will be described in more detail hereinafter. Space 46 is filled with a desired catalyst material 48 of the pellet type with the catalyst material being tightly packed within the space to provide a compact uniform catalyst bed.

In assembly, the mating peripheral flange portions 42 and 44 of the catalyst element 24 are disposed between the peripheral flange portions 20 and 22 of the housing 10 to form a four-layer assembly suitable for edge sealing by means of an external weld 50. In this manner an absolute internal and external seal is provided with the catalyst element 24 mounted and supported within housing 10 and separating an inlet plenum chamber 57 from an outlet plenum chamber 59. In addition the flange portions of housing 10 and catalyst retaining element 24 define an exhaust gas inlet 56 and an exhaust gas outlet 58 in combination with the housing 10. The inlet and outlet are adapted to receive extensions 60, 62, respectively, that can be sealingly joined to the exhaust pipe system of an automobile. It is understood that these connections can be varied, depending on the location of the converter in relation to the exhaust pipe system on the respective automobile on which it is used. A plurality of support studs 100 having shoulders thereon are placed between the top and bottom catalyst retaining plates, with a smaller portion of the studs extending through the top and bottom plates. A plurality of washers 102 are placed over the support studs, and welded in place to retain the high structural integrity that resists deformation and adds strength to the converter.

The catalytic converter thus described has an inclined catalyst bed sloping upwardly from the converter inlet 56 to the converter outlet 58 wherein the exhaust gases entering the converter through the inlet 56 pass through the upper catalyst retaining plate 26 down through the catalyst material 48 and out through the lower catalyst retaining plate 28. Due to the heat present in the converter and the weight of the catalyst on the bottom catalyst retaining plate 28, the bottom catalyst retaining plate may tend to sag in the areas between support studs 100. If the bottom retaining plate sags it closes off or impedes the flow of exhaust gases from the converter through the exhaust outlet 58 thereby creating a back pressure in the engine exhaust system. In accordance with my invention, there is provided means to prevent sag in the designated areas, yet still provide for the full flow of exhaust gases through the entire catalyst bed substantially without any impedance. As described hereinafter in greater detail, a plurality of channels 72 and 74 are attached to the bottom catalyst retaining plate prior to final assembly by means of welding or the like, which, after assembly, are held away from the bottom shell member a minimum distance so that they will not interfere in assembly and in getting a tight outer seam weld.

As best shown in FIG. 2, there are two support channels 72 that are identical in configuration and are located approximately midway between support studs 100 and each side of catalyst retaining element 24 on the bottom catalyst retaining plate 28. In addition, there is a third longer support channel 74 that is located approximately midway between support studs 100 or generally at the center of bottom catalyst retaining plate 28. I have found that the midway location of each of the channels provides the greatest support to the bottom catalyst retaining plate.

The support channel, as best shown in FIG. 6, includes a main elongated flat web section 73 and two upstanding ribs or side walls 78, 79 on the longitudinal sides thereof. Each of the ribs has a plurality of serrations or cutout sections 80 along the outer edges 76, 77 and a plurality of flat sections 82 that join the cutout or serrated sections along the same outer edges, the flat sections defining a sloping plane in relation to the flat section 73 so as to span the vertical space between the bottom plate 34 and the bottom shell 14 as shown in FIG. 3. In securing the channel on plate 28, the serrations are placed adjacent a row of perforations or louvers 36 and are in alignment with and correspond to the perforations to permit the exhaust gases to flow without blockage out of the perforations and through the channel itself to thereby achieve substantially the same basic flow area as that available without the support channels. The channels are formed and sized so there is very little if any impedance of exhaust gas flow. The flat sections 82 that join the serrations or cutout portions in the channels mate with or seat on the flat sections 84 between the perforations 36 to provide a greater area of support to the bottom catalyst retaining plate. Cutout sections 94 and 96 on channel 72 are larger than the other similar sections because of a manufacturing requirement for die relief. Without such relief, the channel 72 is distorted at these sections during the forming operation when the tabs 90, 92, hereinafter described, are formed, whereby in forming the tabs the forming operation pushes the metal outward at sections 94, 96 to effectively make the support channel thicker in these sections with the result that the channel will not fit flat on the bottom catalyst retaining plate 28 due to the distortion at sections 94, 96 which could then prevent the peripheral flange 22 on bottom shell 14 from being drawn against flange 44 to thereby create an assembly problem.

Channels 72 and 74 are tapered at the same angle as the angle of incline of the catalyst bed and are therefore deeper at one end 86 than at the opposite end 88. The support channel also has a pair of struckout portions or tabs 90 and 92 that have bottom webs or legs 91, 93 respectively thereon that are located in the same plane as that of the outer edges 76, 77 of the channel, which tabs are used to locate and secure the support channels on the bottom catalyst retaining plate 28. Tab 90, generally bridge shaped, has a pair of side portions 95 attached to web 91, and ribs 78, 79 to add strength and rigidity to the support channel. Tab 92 is generally formed as an L-shaped member having no side supports and having a web 93 struck upwardly adjacent the upstream end of the converter to define a flat face and a second upstanding web 89 that has longitudinal flexibility. Tab 90 when welded to the bottom catalyst retaining plate will remain rigid and will prevent the support channel from moving while tab 92 having flexibility will permit the support channel to move fore and aft on expansion and contraction relative the bottom catalyst retaining plate due to heating and cooling of the converter. Tab 92 therefore flexes as at 101, FIG. 7, which flexure assures that the welds will not break due to the expansion and contraction of the converter assembly.

In assembly, three support members 72 and 74 are welded on the bottom catalyst retaining plate 28. This is conveniently accomplished by spot welds 97 and 99, FIGS. 5 and 7. A clearance is provided between the bottom shell 14 and the main flat section 73 of the support channel, to assure that when the outer peripheral flanges 20, 22 of the upper and lower shells, and the flanges 42, 44 of the catalyst retaining means are placed together for welding, these flanges will mate and that there will be no displacement due to the use of the support members 72 on the bottom catalyst retaining plate. The clearance is minimal and will vary due to tolerance stack up, but there should be only enough clearance to allow for the flanges to mate without interference to get a good seam weld. In use, the clearance could disappear and the channel would therefore also be supported by the bottom shell 14. These members of the converter are then welded at 50 to provide an integral internal and external seal as has been previously described. An insulating means 104 is placed on the top, and if desired may be placed on the bottom, of the converter and an outer covering or shell 106 is placed over the insulating material to protect it from the elements.

FIG. 8 shows a smaller converter than that shown in FIG. 2 which requires only two long support channels 108 and a shorter support channel 110 adjacent the outlet opening of the converter. The rear tab 92 on the channel is the same as that shown at 92 in FIG. 6 while the front tab 111 though formed the same as tab 90 and for the same reasons, is located at the rear edge of the bottom catalyst retaining plate. The support channel 110 is smaller than the center support channel shown on the converter of FIG. 2 since the two support studs are located along the center line and are sufficient to support the center of bottom plate 28 and to retain the upper and lower shells of smaller housing 10 together. I have found it preferable to provide some support at this rearward location since this is the center of the bottom catalyst support retaining member 28 where sagging could occur. No support is needed at the front of bottom catalyst retaining plate at the inlet end since this is a small area and no significant impedance in the exhaust flow would occur due to sag in this area.

The support channel 72 defines, along its length, a cross sectional area of increasing size, just as does the space between the bottom catalyst retaining member 28 and the bottom shell 14, FIG. 3. Accordingly, the channel tends to carry substantially the same gas flow as would occur in its absence, and the resistance to gas flow through the converter is not substantially affected by the presence of the channel. To minimize the adverse influence of the channel on gas flow, the upstanding portion 89, FIG. 6, upon which welding tab 92 is located, is at the upstream end of the channel, thus reducing the effect of the obstruction to flow that this upstanding portion necessarily creates. Further, the relieved portions 96 of the channel sides adjacent this upstanding portion 89 permit some lateral gas flow around the upstanding portion 89. Further, it will be noted that the welding tab 90 on the downstream end of the channel is formed of a bridge-like arrangement wherein only the thickness of the support is in the way of gas flow. Also, tab 90 is formed at the downstream end, to provide the maximum support area on the channel, at the widest section on the downstream side of the converter.

While the embodiments of the invention as herein disclosed constitute a preferred form, it is to be understood that other forms could be adopted.

Claims

I claim:

1. In a low profile catalytic converter assembly for the treatment of exhaust gas of the type having dished top and bottom housing plates with side wall portions and peripheral flange portions extending outwardly therefrom, a dished catalyst retaining element including top and bottom catalyst retaining plates with peripheral flange portions extending between the flange portions of said top and bottom housing plates for support of said retaining element, an exhaust gas inlet at one end of said assembly and an exhaust gas outlet at the other end of said assembly formed between said peripheral flange portions, a compact bed of catalytic material filling said dished catalyst retaining element in the space between said top and bottom catalyst retaining plates, said retaining plates sloping relative to said housing plates so that the flow area between the upper housing plate and the upper retaining plate decreases as the flow distance from said inlet to said outlet decreases, support studs extending between said top and bottom housing plates and through said top and bottom retaining plates and being anchored to the top and bottom housing plates, the improvement comprising a plurality of elongated channel supports secured to said bottom catalyst retaining plate and extending adjacent to said bottom housing plate, said supports having a flat surface portion extending in parallelism with said bottom housing plate with upstanding rib portions extending from said flat surface toward the bottom catalyst retaining plate between rows of perforations therein and with upstanding web portions forming tabs adapted to attach to said bottom housing plate thus defining open-ended channel means for the passage of exhaust gas therethrough without substantial impedance to the flow.

2. In a low profile catalytic converter assembly for the treatment of exhaust gas of the type having dished top and bottom housing plates with side wall portions and peripheral flange portions extending outwardly therefrom, a dished catalytic retaining element including top and bottom catalyst retaining plates with peripheral flange portions extending between the flange portions of said top and bottom housing plates for support of said retaining element, an exhaust gas inlet at one end of said assembly and an exhaust gas outlet at the other end of said assembly formed between said peripheral flange portions, a compact bed of catalytic material filling said dished catalyst-retaining element in the space between said top and bottom catalyst retaining plates, said retaining plates sloping relative to said housing plates so that the flow area between the upper housing plate and the upper retaining plate decreases as the flow distance from said inlet to said outlet increases, said top and bottom catalyst retaining plates having a plurality of perforations therethrough to permit the flow of exhaust gases between said inlet and outlet through the top retaining plate, the catalytic material and the bottom retaining plate, support studs extending between said top and bottom housing plates and through said top and bottom retaining plates and being anchored to the top and bottom housing plates, the improvement comprising a plurality of elongated channel supports secured to said bottom catalyst retaining plate and extending adjacent to said bottom housing plate, said supports having a flat surface portion extending in parallelism with said bottom housing plate with upstanding rib portions extending from said flat surface toward the bottom catalyst retaining plate between rows of perforations therein thus defining open-ended channel means for the passage of exhaust gas therethrough without substantial impedance to the flow, a first tab portion struck upwardly from said channel supports to define a face web portion abutting the lower retaining plate for attachment thereto and an upstanding web portion in a longitudinal direction, and a second tab portion struck upwardly from said flat surface portion and said side portions to define a bridge-like tab configuration extending across said channel support with a flat face web portion abutting the lower retaining plate for attachment thereto to form a longitudinally rigid support.

3. A low profile catalytic converter assembly for the treatment of exhaust gas of the type having top and bottom cuplike housing shells with side wall portions and peripheral flange portions extending outwardly therefrom, an exhaust gas inlet at one end of the said assembly and an exhaust gas outlet at the other end of said assembly formed between said peripheral flange portions, dished upper and lower catalyst retaining plates forming a catalyst retaining element, said retaining plates sloping relative to said housing shells so that the flow area between the top housing shell and the upper retaining plate decreases as the flow distance from said inlet to said outlet increases, said retaining plates further having peripheral flange portions extending therefrom and supported between the flange portions of said top and bottom shells, a bed of catalyst material filling the space between said dished upper and lower catalyst-retaining plates, said top and bottom catalyst-retaining plates having a plurality of perforations therethrough to permit the flow of exhaust gases between said inlet and outlet through the top retaining plate, the catalytic material and the bottom retaining plate, support studs extending between the top and bottom housing shells and through the top and bottom catalyst-retaining plates at locations approximately one-third the distance in from the side walls of the bottom retaining plate, the improvement comprising support channels secured to said bottom catalyst-retaining plate and extending in longitudinal orientation generally in a direction from said inlet to said outlet, the channels having a substantially flat surface portion in spaced parallelism to the lower shell with a pair of upstanding side walls extending from the flat surface portion toward the lower catalyst-retaining plate, one support channel being located about midway between said support studs, the other support channels being located between the sides of the housing shell and the approximate center of said bottom retaining plate, said upstanding side walls of said channels having alternate serrated and flat sections along an upper edge therefor whereby said flat sections are located adjacent the bottom catalyst-retaining plate between perforations therethrough, a first tab portion struck upwardly from said support channel to define a face web portion abutting the lower retaining plate for attachment thereto and an upstanding web portion having a relatively thin dimension in a longitudinal direction of said channel to permit movement of said face web portion in a longitudinal direction by bending action of said upstanding web portion, each support channel further having a bridge-like tab portion struck upwardly from its bottom surface and side wall portions to define a face web portion abutting the lower retaining plate for connection thereto to form a longitudinally rigid attachment, said serrations being in substantial alignment with and corresponding to perforations in said bottom catalyst-retaining plate to allow exhaust gases to flow through the perforations and serrations and the support channels without substantially impeding the flow of exhaust gases therethrough.

4. A low profile catalytic converter assembly for the treatment of exhaust gas of the type having top and bottom cup-like housing shells with side wall portions and peripheral flange portions extending outwardly therefrom, an exhaust gas inlet at one end of the said assembly and an exhaust gas outlet at the other end of said assembly formed between said peripheral flange portions, dished upper and lower catalyst retaining plates forming a catalyst retaining element, said retaining plates sloping relative to said housing shells so that the flow area between the top housing shell and the upper retaining plate decreases as the flow distance from said inlet to said outlet increases, said retaining plates further having peripheral flange portions extending therefrom and supported between the flange portions of said top and bottom shells, a bed of catalyst material filling the space between said dished upper and lower catalyst-retaining plates, said top and bottom catalyst-retaining plates having a plurality of perforations therethrough to permit the flow of exhaust gases between said inlet and outlet through the top retaining plate, the catalytic material and the bottom retaining plate, support studs extending between the top and bottom housing shells and through the top and bottom catalyst-retaining plates at the approximate center of the converter assembly with said support studs being anchored to the top and bottom housing shells, the improvement comprising at least two support channels secured to said bottom catalyst-retaining plate and extending in longitudinal orientation generally in the direction from said inlet to said outlet, the channels having a substantially flat surface portion in spaced parallelism to the lower housing shell with a pair of upstanding side walls extending upward from the flat surface portion toward the lower catalyst-retaining plate, said support channels being located approximately midway between said support studs and the sides of the housing shell, said side walls of the channels having alternate serrated and flat sections along an upper edge thereof whereby said flat sections are located adjacent the bottom catalyst-retaining plate between perforations therethrough, a first tab portion struck upwardly from said support channel to define a face web portion abutting the lower retaining plate for attachment thereto and an upstanding web portion having a relatively thin dimension in a longitudinal direction of said channel to permit movement of said face web portion in a longitudinal direction by bending action of said upstanding web portion, each support channel further having a bridge-like tab portion struck upwardly from its bottom surface and side wall portions to define a face web portion abutting the lower retaining plate for connection thereto to form a longitudinally rigid attachment, said serrations being in substantial alignment with and corresponding to perforations in said bottom catalyst-retaining plate to allow exhaust gases to flow through the perforations and serrations and the support channels without substantially impeding the flow of exhaust gases therethrough.