Patent ID: 8512562

Claim:
A drain mechanism for a fluid filter, comprising: a cap that is attached detachably to a case of a fluid filter and formed with a drain hole, and includes an engaging projecting portion to which an engaging portion of a drain pipe inserted into said drain hole is engaged, said engaging projecting portion including an inclined rear side surface thereof and a contact end of said inclined rear side surface to which a contact tip end of said engaging portion of said drain pipe is engaged; and a valve member that is provided in the interior of said cap so as to close said drain hole and displaced in a direction for releasing closure of said drain hole upon contact with a tip end portion of said drain pipe inserted into said drain hole, wherein said valve member is provided with a holding recess portion for holding said tip end portion of said drain pipe, a planar contact portion contacted by said tip end portion of said drain pipe is provided inside said holding recess portion of said valve member, an open end of said holding recess portion of said valve member is defined by the plane formed by the planar contact portion, an interval between said contact end of said inclined rear side surface of said engaging projecting portion to which said contact tip end of said engaging portion is engaged and the open end of said holding recess portion of said valve member defines an interval (A), and an interval between said contact end of said inclined rear side surface of said engaging projecting portion to which said contact tip end of said engaging portion is engaged and said tip end portion of said drain pipe, when a tip end side of said engaging portion of said drain pipe inserted into said drain hole is in contact with said inclined rear side of said engaging projecting portion of said cap, defines an interval (B), such that with said tip end side of said engaging portion of said drain pipe inserted into said drain hole in contact with said inclined rear side of said engaging projecting portion of said cap, said interval (A) is longer than said interval (B).