Patent ID: 7083660

Claim:
A casing member comprising: a main body having a first vent hole extending through said main body, a sheet joining part surrounding said first vent hole at a periphery of said first vent hole, and a cover insert member receiving recess surrounding said sheet joining part at a periphery of said sheet joining part; a cover insert member having a main portion and an annular protrusion protruding from said main portion in a thickness direction of said main portion, said annular protrusion being located within said cover insert member receiving recess of said main body so that said cover insert member is joined to said main body, and having a second vent hole extending through said cover insert member, said second vent hole having a smaller cross-sectional area than said first vent hole; and a permeable sheet for allowing permeation of a gas therethrough and for preventing permeation of a liquid therethrough, said permeable sheet having a first surface and a second surface opposite said first surface, said permeable sheet being arranged so that a peripheral portion of said first surface is bonded to said main body and so that a peripheral portion of said second surface contacts said cover insert member such that a peripheral portion of said permeable sheet is held between said main body and said cover insert member, said permeable sheet being arranged so as to cover said first vent hole, and said first vent hole of said main body and said second vent hole of said cover insert member being arranged to communicate with each other through said permeable sheet.