Abstract:
A catalytic converter and method for its assembly including an external shell formed in two halves containing a catalytic substrate, two internal shields and two-piece inlet and outlet cones. The inlet and outlet cones are attached as halves to each side of the external shell, and are assembled to each other as the external shells are assembled.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a catalytic converter, more particularly, the present invention is related to a method of attaching the internal shields in an automotive catalytic converter and catalytic converter assembly. 
     DESCRIPTION OF PRIOR ART 
     Vehicles that run on fossil fuels are a source of air pollution throughout the world. Modern vehicle engines carefully control the amount of fuel they burn, but the combustion is not perfect and some undesirable emissions are produced in car engines such as carbon monoxide, hydrocarbons and nitrogen oxides. 
     To reduce emissions, vehicles use a device called a catalytic converter to treat the engine emissions. Catalytic converters typically incorporate a ceramic substrate coated with a metal catalyst such as platinum or palladium. The catalysts promote further combustion and chemical reactions to change the carbon monoxide, hydrocarbon and nitrogen oxide molecules to non-harmful molecules. The chemical process occurring in the catalytic converter are exothermic reactions, releasing heat into the exhaust gas stream and the converter housing. 
     Catalytic converters traditionally contain an external shell that surrounds the substrate and inlet and outlet cone assemblies that attach the catalytic converter to the vehicle exhaust pipes or components. Heat shields are provided to prevent overheating of the floor pan, which is undesirable for the vehicle occupants and further to reduce the likelihood of initiating combustion of materials below the vehicle. The internal cones (or internal shields) are generally one-piece or two-piece designs that are spot welded to the external shell at the inlet and outlet of the converter assembly. The two halves of the external shell are then pressed together into the proper assembly position and finally welded. 
     The current design has several main problems associated with locating of the internal cones and substrate and the external shell gaps. When the external shells are pressed together, it is difficult to locate the internal shields, which is the first problem. The second concern occurs when the substrate sizes vary significantly. When this occurs, it is difficult to close the gap between the external shell and the substrate due to the existence of the internal shields. A further problem with previous designs is that manufacturers do not weld the internal portion of the cone to the external shell. This can cause a noise and vibration problem and also potentially damage the ceramic substrate. 
     Therefore, there is a need in the automotive industry, as well as in other industries, for an improved process of attaching the internal shields of a catalytic converter to the external shells. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the present invention, the internal cones can be manufactured in two halves, similar to the external shells. The external shells have perimeter flanges for attaching the shields together at the final step of the process. Each half of an internal cone is spot welded in a pocket on each side of each half of the external shell. This attachment supports and locates the internal cone. The substrate is then located in between the internal cones on the external shell. The two halves of the external shell can then be welded together at its perimeter flanges. 
     The assembly of the internal cone halves and the external shell halves is made when perimeter flanges are raised on one half of the shell to fit over straight flanges on the other half of the shell. The design is similar to how a shoebox lid fits over the main shoebox. 
     Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is top view of the straight cone type catalytic converter of the present invention; 
         FIG. 2  is a bottom view of  FIG. 1 ; 
         FIG. 3  is a side sectional view of  FIG. 1  cut through line A-A; 
         FIG. 4  is a side sectional view of  FIG. 1  cut through line B-B; 
         FIG. 5  is a top view of the catalytic converter of the present invention with the external shell removed; 
         FIG. 6  is a top view of an alternate embodiment of the catalytic converter of the present invention with offset cones; and 
         FIG. 7  is a top view of a further embodiment of the catalytic converter of the present invention with oblique cones. 
     
    
    
     DETAILED DESCRIPTION 
     The foregoing discussion discloses and describes the preferred embodiment of the invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that changes and modifications can be made to the invention without departing from the true spirit and fair scope of the invention as defined in the following claims. The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. 
     Referring now to  FIG. 1 , a top view of the catalytic converter  10  of the present invention is shown. Internal cones  80  and  82  and catalytic substrate  48  (shown in  FIG. 5 ) are contained by the external shell  12  of the catalytic converter  10 . The external shell  12  is a two piece design and is made up of external shell top  40  and external shell bottom  42  (shown in  FIG. 3 ). The external shell  12  contains inlet  14  and outlet  16 , which attach to exhaust system piping (not shown). Inlet  14  and outlet  16  are substantially centered along inlet side  13  and outlet side  15  of external shell  12 . Engine emissions enter the catalytic converter  10  through inlet  14 , are treated by the catalytic substrate  48  and exit through outlet  16 . The inlet end  14 , outlet end  16 , and external shell  12  are aligned about a central axis  19 . 
     Inlet  14  and outlet  16  are the narrowest points on external shell  12  of the catalytic converter  10 . From inlet  14 , the external shell  12  widens through widening sides  18  and  20 , which are of substantially the same length. Widening sides  18  and  20  end at straight sides  26  and  28 , respectively. The external shell  12  of the catalytic converter  10  reaches its widest point along straight sides  26  and  28 , which are also of substantially the same length. The straight sides  26  and  28  extend at least the length of the catalytic substrate  48  until narrowing sides  22  and  24 , respectively, are reached. The narrowing sides  22  and  24  are of substantially the same length. The external shell  12  then narrows again along narrowing sides  22  and  24  until outlet  16  is reached. 
     Inlet internal cone  80  and outlet internal cone  82 , shown by shadowed lines in their location inside external shell top  40 , are also two-piece designs. Inlet internal cone  80  contains tabs  41  and  43  on inlet internal cone top  44 . Outlet internal cone  82  contains tabs  45  and  47 . Attachment tabs  17 ,  19 ,  21  and  23  are recessed on external shell top  40 . Inlet internal cone  80  tabs  41  and  43  is attached to the external shell top  40  at attachment points  17  and  19  on external shell top  40 , respectively, by a manufacturing process such as spot welding, although other manufacturing processes are possible. Similarly, outlet internal cone  82  tabs  45  and  47  are attached to external shell top  40  at attachment points  21  and  23 , respectively. 
     The inlet internal cone top  44  and external shell top  40  are also attached, by spot welding or a similar process, at inlet side  13  at the inlet  14  of the catalytic converter  10  at attachment points  51  and  53 . Similarly, the outlet internal cone top  45  and external shell top  40  are attached at outlet side  15  of the catalytic converter  10  at attachment points  55  and  57 . 
     Now referring to  FIG. 2 , a bottom view of the catalytic converter  10  of the present invention is shown. Inlet internal cone  80  contains tabs  41   a  and  43   a  on inlet internal cone bottom  46 . Outlet internal cone  82  has an external internal shield bottom  30 , which contains tabs  45   a  and  47   a . Attachment points  17   a ,  19   a ,  21   a  and  23   a  are recessed on external shell bottom  42 . Tabs  41   a  and  43   a  are attached to the external shell bottom  42  at attachment points  17   a  and  19   a  on external shell bottom  42 , respectively. Similarly, tabs  45   a  and  47   a  on the outlet internal shield bottom  30  are attached to external shell bottom  42  at attachment points  21   a  and  23   a , respectively. 
     The inlet internal cone bottom  46  and external shell bottom  42  are also attached, by spot welding or a similar process, at inlet side  13  at the inlet  14  of the catalytic converter  10  at attachment points  51   a  and  53   a . Similarly, the outlet internal cone bottom  45  and external shell bottom  42  are attached at outlet side  15  of the catalytic converter  10  at attachment points  55   a  and  57   a.    
     Now referring to  FIG. 3 , a side sectional view of the catalytic converter  10  is shown through the lengthwise line A-A of the external shell top  40  and internal cone top  44 . The external shell  12  has external shell top  40 . The internal cone  80  has inlet internal cone top  44 . At inlet side  13 , the external shell top  40  contains attachment flange  31 , which is recessed in external shell top  40  and the inlet internal cone top  44  contains attachment flange  33 . The external shell top  40  is attached to the inlet internal cone top  44  by joining attachment flanges  31  and  33  together by a method such as spot welding. 
     Similarly, the external shell top  40  is attached to the inlet internal cone top  44  at tab  41 , which is also recessed in the external shell top  40  on the inlet internal cone top  44 . Tab  41  is joined, by spot welding or a similar process, to the external shell top at attachment point  17 . 
     Now referring to  FIG. 4  a side sectional view through width line B-B of the catalytic converter  10  is shown. External shell  12  is made up of two pieces, external shell top  40  and external shell bottom  42 . Inlet internal cone  80  is also made up of two pieces, internal cone top  44  and internal cone bottom  46 . External shell top  40  encases internal cone top  44 . External shell bottom  42  encases internal cone bottom  46 . 
     To aid assembly, the external shell top  40  and external shell bottom  42  contain straight and raised end flanges. The external shell top  40  contains straight flange  50  and straight flange  54  and the external shell bottom  42  contains raised flange  56  and raised flange  52 . When the external shell  12  is assembled as one piece, raised flange  52  of external shell bottom  42  fits atop straight flange  50  of external shell top  40 . On the opposite side of external shell  12 , straight flange  54  of external shell bottom  40  sits beneath raised flange  56  of external shell bottom  42 . 
     Concurrent with the assembly of external shell  12 , inlet internal cone  80  is assembled. To aid assembly of the internal cone top  44  and internal cone bottom  46 , the internal cone top  44  contains straight flange  60  and raised flange  64  and the internal cone bottom  46  contains straight flange  66  and raised flange  62 . When the internal cone  12  is assembled, raised flange  62  of internal cone bottom  46  fits atop straight flange  60  of internal cone top  44 . On the opposite side of internal cone  12 , raised flange  64  of internal cone bottom  44  sits atop straight flange  66  of internal cone bottom  46 . 
     Now referring to  FIG. 5 , a top view of the catalytic converter  10  is shown with the external shell  12  removed. Catalytic substrate  48  sits between inlet internal cone  80  and outlet internal cone  82 . 
     Similar to the shape of external shell  12 , inlet internal cone  80  has its narrowest point at inlet  14 . From inlet  14 , the internal inlet cone  80  widens through widening sides  84  and  86 , which are substantially of the same length. Widening sides  84  and  86  end at straight sides  88  and  90 , respectively. Straight sides  88  and  90  are of substantially the same length. The internal inlet cone  80  of the catalytic converter  10  reaches its widest point along straight sides  88  and  90 . The straight sides  88  and  90  end at internal side  72 . Internal side  72  of internal inlet cone  80  mates with inlet side  76  of the catalytic substrate  48 . 
     On the opposite side of catalytic substrate  48 , exit side  78  of the catalytic substrate  48  mates with internal side  74  of the outlet internal cone  82 . Straight sides  96  and  98 , which are of substantially the same length, of outlet internal cone  82  extend from the internal side  74  and are the widest point of outlet internal cone  82 . Straight sides  96  and  98  end at narrowing sides  92  and  94 , respectively. The narrowing sides  92  and  94 , which are of substantially the same length, narrow the width of the outlet internal cone  82  until outlet  16  is reached, which is the outlet internal cone&#39;s  82  narrowest point. 
     Now referring to  FIG. 6 , an alternate embodiment of the present invention is shown in a top view. Catalytic converter  110  contains external shell  112  with inlet  114  and outlet  116 . Inlet  114  and outlet  116  are the narrowest points on catalytic converter  110 . 
     From inlet  114 , the external shell  112  widens through widening sides  118  and  120 , which are of differing lengths. In this embodiment, widening side  118  is substantially longer than widening side  120 , offsetting the location of inlet  114  along inlet side  113  of external shell  112 . Widening sides  118  and  120  end at straight sides  126  and  128 , respectively. 
     The external shell  112  of the catalytic converter  110  reaches its widest point along straight sides  126  and  128 , which can be of the same or substantially different lengths. Straight side  126  is shorter than straight side  128  in this embodiment. The straight sides  126  and  128  extend at least the length of the catalytic substrate  48  until narrowing sides  122  and  124 , respectively, are reached. The narrowing sides  122  and  124  can be the same or of substantially different lengths. In this embodiment, narrowing side  122  is longer than narrowing side  124 . The external shell  112  then narrows again along narrowing sides  122  and  124  until outlet  116  is reached. Outlet  116  is offset from center along exit side  115  of external shell  112 . 
     Now referring to  FIG. 7 , a further embodiment of the present invention is shown in a top view. Catalytic converter  210  contains external shell  212  with inlet  214  and outlet  216 . Inlet  214  and outlet  216  are the narrowest points on catalytic converter  210 . 
     From inlet  214 , the external shell  212  widens through widening sides  218  and  220 , which are of differing lengths. In this embodiment, widening side  218  is an arc shape and is substantially longer than widening side  220 , which is also of an arc shape. The location of inlet  214  is at an oblique angle along inlet side  213  of external shell  212 . Widening sides  218  and  220  end at straight sides  226  and  228 , respectively. 
     The external shell  212  of the catalytic converter  210  reaches its widest point along straight sides  226  and  228 , which are of substantially the same or different lengths. The straight sides  226  and  228  extend at least the length of the catalytic substrate  48  until narrowing sides  222  and  224 , respectively, are reached. The narrowing sides  222  and  224  are of substantially different lengths. In this embodiment, narrowing side  222  is an arc shape and is longer than narrowing side  224 , which is also an arc shape. The external shell  212  then narrows again along narrowing sides  222  and  224  until outlet  216  is reached. Outlet  216  is at an oblique angle along exit side  215  of external shell  212 . 
     While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.