Stepped down aftertreatment device shroud

Abstract

A shroud ( 102 ) for an aftertreatment device ( 100 ) for treating exhaust gas from an internal combustion engine comprises a stepped conduit ( 126 ) configured to be disposed over an upper surface of the aftertreatment device ( 100 ) and extending over substantially the entire length of the aftertreatment device ( 100 ), wherein the stepped conduit ( 126 ) is configured to channel a flow of cleaning air longitudinally along the outer and upper surface of the aftertreatment device ( 100 ), wherein an inner surface of the stepped conduit ( 126 ) defines at least a first downwardly extending step ( 134, 136, 138 ) and a second downwardly extending step ( 134, 136, 138 ) that are spaced apart along the length of the aftertreatment device ( 100 ), to direct at least a portion of the flow of cleaning air downward.

I claim: 
     
         1 . A shroud ( 102 ) for an aftertreatment device ( 100 ) for treating exhaust gas from an internal combustion engine, the shroud comprising:
 a stepped conduit ( 126 ) configured to be disposed over an upper surface of the aftertreatment device ( 100 ) and extending over substantially an entire length of the aftertreatment device ( 100 ), wherein the stepped conduit ( 126 ) is configured to channel a flow of cleaning air longitudinally along an outer and upper surface of the aftertreatment device ( 100 ), wherein an inner surface of the stepped conduit ( 126 ) defines at least a first downwardly extending step ( 134 ,  136 ,  138 ) and a second downwardly extending step ( 134 ,  136 ,  138 ) that are spaced apart along a length of the aftertreatment device ( 100 ), to direct at least a portion of the flow of cleaning air downward.   
     
     
         2 . The shroud ( 102 ) of  claim 1 , further comprising a first sidewall ( 118 ) that is fixed to the stepped conduit ( 126 ) along a first longitudinal side edge of the stepped conduit ( 126 ), wherein the first sidewall ( 118 ) extends around and encloses a first side surface of the aftertreatment device ( 100 ), wherein the first sidewall ( 118 ) is disposed to provide a narrow gap ( 128 ) between the first sidewall ( 118 ) and the first side surface of the aftertreatment device ( 100 ) to receive the flow of cleaning air from the stepped conduit ( 126 ) over substantially the entire length of the aftertreatment device ( 100 ) and to direct the flow of cleaning air generally downward over the first side surface of the aftertreatment device ( 100 ). 
     
     
         3 . The shroud ( 102 ) of  claim 2 , further comprising a second sidewall ( 120 ) that is fixed to the stepped conduit ( 126 ) along a second longitudinal side edge of the stepped conduit ( 126 ) and is disposed on an opposite side of the stepped conduit ( 126 ) from the first sidewall ( 118 ), wherein the second sidewall ( 120 ) extends around and encloses a second side surface of the aftertreatment device ( 100 ), wherein the second sidewall ( 120 ) is disposed to provide a narrow gap ( 130 ) between the second sidewall ( 120 ) and the second side surface of the aftertreatment device ( 100 ) to receive the flow of cleaning air from the stepped conduit ( 126 ) over substantially the entire length of the aftertreatment device ( 100 ) and to direct the flow of cleaning air generally downward over the second side surface of the aftertreatment device ( 100 ). 
     
     
         4 . The shroud ( 102 ) of  claim 1 , wherein the aftertreatment device ( 100 ) is elongate, generally cylindrical, and has a central longitudinal axis ( 104 ) that extends generally horizontally. 
     
     
         5 . The shroud ( 102 ) of  claim 4 , wherein the aftertreatment device ( 100 ) has a top surface, and wherein the stepped conduit ( 126 ) extends generally horizontally and is disposed immediately over the top surface of the aftertreatment device ( 100 ). 
     
     
         6 . The shroud ( 102 ) of  claim 5 , wherein the first downwardly extending step ( 134 ,  136 ,  138 ) and the second downwardly extending step ( 134 ,  136 ,  138 ) are disposed above the top surface of the aftertreatment device ( 100 ) and are spaced apart along the top surface of the aftertreatment device ( 100 ). 
     
     
         7 . The shroud ( 102 ) of  claim 6 , wherein the first downwardly extending step ( 134 ,  136 ) is disposed immediately downstream of a first protrusion ( 150 ,  152 ) that extends upwardly from the top surface of the aftertreatment device ( 100 ). 
     
     
         8 . The shroud ( 102 ) of  claim 7 , wherein the second downwardly extending step ( 134 ,  136 ) is disposed immediately downstream of a second protrusion ( 150 ,  152 ) that extends upwardly from the top surface of the aftertreatment device ( 100 ). 
     
     
         9 . The shroud ( 102 ) of  claim 8 , wherein each of the first protrusion ( 150 ,  152 ) and the second protrusion ( 150 ,  152 ) comprises an annular ring extending about a circumference of the aftertreatment device ( 100 ).