Exhaust after treatment assembly

Abstract

The invention relates to an exhaust after treatment assembly. There is a need for such assembly which remains as cool as possible. An exhaust after treatment assembly includes a hollow housing containing an exhaust after treatment unit. The housing forms a nozzle which directs exhaust gases away from the after treatment unit. A shield surrounds and is spaced apart from the housing. A venturi unit receives exhaust gases from the nozzle and receives outside air. The venturi unit pulls outside air over an exterior of the shield and mixes the outside air with exhaust gases flowing though the after treatment unit. The venturi unit is mounted inside a hood which surrounds part of the housing. Outside air is drawn through an annular gap which is formed between an end of the hood and an end of the shield.

1 . An exhaust after treatment assembly, comprising:
 a hollow housing containing an exhaust after treatment unit;   a nozzle for directing exhaust gases away from the after treatment unit;   a shield surrounding and spaced apart from the housing; and   a venturi unit receiving exhaust gases from the nozzle and receiving outside air, the venturi unit operating to pull outside air over an exterior of the shield and to mix said outside air with exhaust gases flowing though the after treatment unit.   
     
     
         2 . The exhaust after treatment assembly of  claim 1 , further comprising:
 a hood having an inlet end, an outlet end and a tubular portion connecting the inlet end to the outlet end, the venturi unit being mounted inside the tubular portion, the inlet end being spaced apart from and surrounding an end of the shield and forming an annular gap therebetween, the venturi unit drawing outside air through said gap.   
     
     
         3 . The exhaust after treatment assembly of  claim 2 , wherein:
 the hood comprises a tapered portion connected between the inlet end and the tubular portion.   
     
     
         4 . The exhaust after treatment assembly of  claim 1 , wherein:
 the housing includes a main portion surrounding the after treatment unit and a conical portion connecting the main portion to the nozzle.   
     
     
         5 . The exhaust after treatment assembly of  claim 1 , wherein:
 the venturi unit comprises a larger diameter entry surrounding a downstream end of the nozzle, a smaller diameter neck downstream of the entry and a larger diameter exit downstream of the neck.   
     
     
         6 . An exhaust after treatment assembly, comprising:
 a hollow housing having a central portion containing an exhaust after treatment unit, an inlet end for communicating engine exhaust gases to the after treatment unit and having an outlet for directing exhaust gases away from the after treatment unit, the outlet having a nozzle and a conical portion connecting the nozzle to an end of the central portion;   a shield surrounding and spaced apart from the central portion of the housing; and   a hood having an inlet end surrounding a downstream end of the shield, a tapered portion connected to the inlet end and surrounding the conical portion and the nozzle, a tubular portion connected to a downstream end of the tapered portion and extending to an outlet remote from the tapered portion; and   the tubular portion having a venturi unit therein, the venturi unit having a larger diameter entry surrounding a downstream end of the nozzle, a smaller diameter neck downstream of the entry and a larger diameter exit downstream of the neck, the venturi operating to pull outside air over an exterior of the shield, over the an exterior of the conical portion and the nozzle and to mix said outside air with exhaust gases flowing though the after treatment unit.