Exhaust gas muffler for an internal combustion engine

Abstract

An exhaust gas muffler for an internal combustion engine is provided, especially for a portable implement. The muffler has a housing with at least two parts, an inlet for exhaust gas issuing from the engine, and an outlet for discharge of processed exhaust gas. A partition is disposed within the housing between the inlet and outlet and divides the housing into two chambers. The partition is provided with a first opening in which a catalyzer is mounted, and at least one bypass opening. The muffler also has a respective valve member for each bypass opening. Below a specified temperature the bypass opening is closed. The valve member is controlled by the temperature in the muffler in such a way that when a prescribed operating temperature is exceeded, the bypass opening is opened.

What we claim is:  
     
         1 . An exhaust gas muffler for an internal combustion engine comprising: 
 a housing having at least two parts an inlet for exhaust gas issuing from said internal combustion engine, and an outlet for a discharge of processed exhaust gas to the atmosphere;    a partition disposed within said housing between said inlet and said outlet and dividing said housing into two chambers, wherein said partition is provided with a first opening and at least one bypass opening;    a catalyzer mounted in said first opening of said partition; and    a respective valve member for said at least one bypass opening, wherein below a specified temperature said at least one bypass opening is closed and wherein said valve member is controlled by the temperature in said muffler such that when a prescribed operating temperature therein is exceeded, said at least one bypass opening is opened.    
     
     
         2 . An exhaust gas muffler according to  claim 1 , wherein said valve member is thermoelectrically controlled.  
     
     
         3 . An exhaust gas muffler according to  claim 1 , wherein said valve member is a bimetal strip.  
     
     
         4 . An exhaust gas muffler according to  claim 1 , wherein said valve member is disposed on a side of said partition that faces said inlet of said housing.  
     
     
         5 . An exhaust gas muffler according to  claim 1 , wherein a plurality of bypass openings are disposed in said partition.  
     
     
         6 . An exhaust gas muffler according to  claim 1 , wherein said valve member can assume two operating positions, and wherein upon reaching a prescribed temperature said valve member is brought from a position where said at least one bypass opening is completely closed into a position in which said at least one bypass opening is completely opened.  
     
     
         7 . An exhaust gas muffler according to  claim 1 , wherein after a predetermined temperature threshold said valve member partially opens said at least one bypass opening, and during a further increase in temperature said valve member increases a passage cross section of said at least one bypass opening.