Patent ID: 7435345

Claim:
An element replacement type filter that accommodates an element assembly that includes a filter element within a casing formed from a first casing member and a second casing member which are mutually screwable by relative rotation, and that provides an anti-loosening mechanism between said first casing member and said second casing member, wherein said anti-loosening mechanism comprises a regulating portion that is provided on an outer peripheral side of said first casing member; and a leaf spring member made of metal that is provided elastically deformable in a radial direction of said second casing member, with a base end side thereof fixed to an outer peripheral side of said second casing member, and said leaf spring member has a free end side that is provided with a contact portion, which contacts said regulating portion due to relative rotation of said first casing member and said second casing member, wherein said contact portion comprises: a first contact surface that contacts said regulating portion when said first casing member and said second casing member are relatively rotated in directions that tighten screwing thereof; and a second contact surface that contacts said regulating portion when said first casing member and said second casing member are relatively rotated in directions that loosen screwing thereof, wherein an angle formed by said first contact surface and a tangent of said second casing member is set to a value smaller than an angle formed by said second contact surface and the tangent of said second casing member.