Muffler with improved heat dissipation

Abstract

A muffler has inner and outer elongated concentric and radially spaced generally cylindrical casings having inlet and outlet ends, and providing an annular chamber therebetween. The outer casing has an inlet opening into the annular chamber adjacent the inlet end of the outer casing so that air may flow to the outer end. The inner casing has an aperture adjacent the outlet end for the air to flow from the annular chamber into the inner casing for discharge with the exhaust. This air flow through the annular chamber reduces the temperature of the outer casing from that of the inner casing. Baffles are provided in the inner casing, and insulating material may also be provided in the inner casing.

1 . A muffler and exhaust extractor comprising: 
 (a) an inner elongated generally cylindrical casing having inlet and outlet ends;    (b) an outer elongated generally cylindrical casing having inlet and outlet ends, the diameter of said outer casing being greater than that of said inner casing to provide an annular chamber therebetween;    (c) an exhaust inlet fitting at the inlet end of said inner casing;    (d) an air inlet adjacent the inlet end of said outer casing to allow air to flow into said annular chamber;    (e) vents in said inner casing adjacent said outlet end thereof to permit air to flow from said annular chamber into the exhaust flowing through said inner casing; and    (f) baffle elements in said inner casing, whereby exhaust flows through said inner casing about said baffle elements and ambient air flows through said annular chamber to provide a temperature at said outer casing which is lower than that of said inner casing.    
   
   
       2 . The muffler and exhaust extractor in accordance with  claim 1  wherein the inlet end of said inlet fitting is of lesser diameter than said inner casing and has an outwardly sloping wall extending to said inner casing.  
   
   
       3 . The muffler and exhaust extractor in accordance with  claim 2  wherein said outer casing has an inner end portion extending over a portion of said outwardly sloping wall of said inlet fitting and said air inlet is provided in said inner end portion of said outer casing.  
   
   
       4 . The muffler and exhaust extractor in accordance with  claim 3  wherein the end of said inner end portion of said outer casing is secured to said sloping wall of said inlet fitting.  
   
   
       5 . The muffler and exhaust extractor in accordance with  claim 1  wherein there is included an end cap at the outlet-end of said casings and wherein said casings are supported thereon.  
   
   
       6 . The muffler and exhaust extractor in accordance with  claim 1  wherein said baffle elements comprise: 
 (a) a generally frustoconical baffle in said inner casing adjacent said inlet end, said frustoconical baffle being elongated with the smaller diameter portion being spaced from said inlet end, the peripheral wall of said baffle having perforations therein closely spaced about the periphery and over the major portion of the axial length thereof, said baffle being spaced from said inner casing over the major portion of its axial length to provide an inlet end inner chamber thereabout; and    (b) a generally cylindrical baffle in said inner casing having one end extending over the smaller diameter portion of said frustoconical baffle, said cylindrical baffle having its peripheral wall spaced from said inner casing over substantially the entire length thereof to provide an elongated inner chamber thereabout communicating with said inlet end inner chamber about said frustoconical baffle, said peripheral wall having closely spaced perforations extending circumferentially thereabout and over the major portion of its length, whereby a substantial portion of the volume of exhaust gases entering the inlet end of said frustoconical baffle exits through said perforations in said peripheral wall and thence moves generally axially in said chamber thereabout and into said chamber about said cylindrical baffle, the exhaust gases then passing into said cylindrical baffle through said apertures therein and moving axially therethrough to said exit end of said casing.    
   
   
       7 . The muffler and exhaust extractor in accordance with  claim 6  wherein the end of the smaller diameter portion of said frustoconical baffle is open so that some of the exhaust gases pass axially therethrough into the interior of said cylindrical baffle.  
   
   
       8 . The muffler and exhaust extractor in accordance with  claim 6  wherein the apertures in the peripheral wall of said cylindrical baffle are oriented in a spiral pattern.  
   
   
       9 . The muffler and exhaust extractor in accordance with  claim 6  wherein the inlet end of said frustoconical baffle is supported by said inlet fitting which has an outwardly extending generally cylindrical portion for connection to an element of the exhaust system.  
   
   
       10 . The muffler and exhaust extractor in accordance with  claim 9  wherein the inlet end of said inner casing is secured to the outer surface of said end cap.  
   
   
       11 . The muffler and exhaust extractor in accordance with  claim 6  wherein said outlet end of said cylindrical baffle is supported by an end cap in said inner casing adjacent said outlet end thereof.  
   
   
       12 . The muffler and exhaust extractor in accordance with  claim 6  wherein there is included heat-resistant fibrous material in said elongated inner chamber to enhance sound reduction.