US Patent 10196948 Exhaust muffler for combustion engine

A muffler for decreasing the amount of noise of exhaust gases from a combustion engine is fluid connected with an exhaust port of an engine cylinder through an exhaust pipe. The interior of the muffler is divided into a first expansion chamber on the most upstream side, and a second expansion chamber on a downstream side thereof. The exhaust pipe is fluid connected with the muffler so as to be present within the first expansion chamber. The muffler is furthermore provided with a cooling pipe, which extends through the first expansion chamber, and a cooling air flows through cooling pipe.