Ceramic filters for diesel exhaust particulates

Claim 1

A compact through flow exhaust particulate filter element for diesel engines, said element comprising a ceramic monolith having a plurality of interlaced thin gas filtering porous internal walls defining a plurality of parallel passages extending to opposite ends of the element, said passages including a first group comprising inlet passages open at one end of the element and closed at the other and a second group comprising outlet passages closed at said one end of the element and open at the other, wherein the said inlet and outlet passages are arranged such that each non-engaged portion of every interior wall in the element lies between an inlet passage and an outlet passage and forms a filtration surface for gas flow between them, the porosity of the walls being sized to filter out a substantial portion of particulates present in diesel exhaust gases passed through the element from the inlet to the outlet passages and the improvement wherein the inlet passages have individual and collective cross-sectional areas substantially greater than the respective individual and collective cross-sectional areas of the outlet passages to provide a significant volume for collection of particulates in the filter element inlet passages without reduction of their effective flow area below that of the outlet passages.