Enclosed-type magnetic disc recording and/or reproducing apparatus

Claim 1

An enclosed-type magnetic disc recording and/or reproducing apparatus for use in conjunction with a magnetic disc, comprising: a base; a disc cover attached to said base and defining an enclosed chamber between said cover and said base; a bearing unit having a first end protruding into said enclosed chamber from said base and a second end exposed to open air; a shaft supported by said bearing unit and having a tip end protruding into said enclosed chamber; a flange attached to the tip end of said shaft and adapted to have said disc attached thereto; a first cylindrical projecting member projecting toward said flange from said base concentrically with said shaft; a second cylindrical projecting member projecting toward said base from said flange and overlapping said first cylindrical projecting member to form a narrow gap between the overlapping portions of said cylindrical projecting members, whereby a separate pressure chamber surrounded by said flange, said base and both cylindrical projecting members is formed; means for rotating said shaft, said flange, said disc, and said second cylindrical projecting member; and a pressure supply system for introducing high-pressure air into said separate pressure chamber through an air inlet bored in said base, at least during operation of said recording and/or reproducing apparatus; wherein said gap between the overlapping portions of said first and second cylindrical projecting members is sufficiently narrow and sufficiently long to restrict air leakage from said separate pressure chamber through said gap to maintain said separate pressure chamber at higher than atmospheric pressure.