Soot filter for cleaning the exhaust from an internal combustion engine

Claim 1

A soot filter for cleaning an exhaust gas stream of an internal combustion engine, said filter comprising a plurality of axially parallel filter tubes arranged in a circle in a filter housing, said tubes being formed of refractory ceramic yarn wound to form hollow cylinders through which exhaust flows radially inwardly, said tubes each being closed at one end and provided at its other end with a clean gas outlet opening, said filter housing having at least one inlet chamber into which the closed ends of the filter tubes project and at least one clean-gas manifold chamber in communication with the clean gas outlet openings of said tubes, wherein adjacent tubes are spaced apart a distance (A) which corresponds to from about 2 to about 4% of the average outside diameter (D) of the filter tubes, and wherein an elongated electrical heating element (37) is disposed in each interstice (36, 42, 43) formed by at least three filter tubes (30), and means are provided for energizing said electrical heating element when the exhaust gas stream through said filter tubes is interrupted.