Radial flow type dust collecting filter

Claim 1

A radial flow type dust collecting filter provided with a cylindrical filtering wall of substantially constant radial thickness for filtering fluid flowing in the radial inward direction of said filtering wall, comprising: a thin walled first filter member of generally cylindrical shape and having a generally zig-zag or corrugated configuration in longitudinal section to define circumferentially-extending inwardly-facing and outwardly-facing ridges separated by inwardly-facing and outwardly-facing valley-like spaces, said ridges having end portions connected to main portions of said first filter member; a second filter member which is disposed within and completely fills the outwardly-facing spaces defined by said first filter member; a third filter member which is disposed within and completely fills the inwardly-facing spaces defined by said first filter member, which interiorly covers said first filter member and which has a cylindrical interior surface defining an axially extending through hole in the center thereof; and a pair of end plates which are fixed to both axial ends of said first and third filter members, respectively, for retaining said filter members therebetween, at least one of said end plates having a central hole in communication with said through hole, at least said end portions of one of said inwardly-facing and said outwardly-facing ridges having a flowing resistance larger than that of said main portions of said first filter member, and each of said second filter member and said third filter member having generally the same flowing resistance smaller than that of said main portions of said first filter member for collecting dust primarily by impaction.