Magnetic disk cartridge with improved center plate for disk mounting

Claim 1

In a disk cartridge comprising a sheet-like, flexible recording medium fixed to the periphery of a circular center plate in which a substantially square center hole and a substantially rectangular eccentric driving hole are provided, and a cartridge rotatably accommodating the sheet-like, flexible recording medium and including an upper half and a lower half having a turntable insertion hole in which said circular center plate is loosely fitted; the improvement comprising a synthetic resin ring formed integrally and coaxially with said circular center plate on the upper side thereof and having a small diameter relative to said center plate so as to surround said substantially square center hole, said substantially square center hole of the circular center plate having an upstanding flange extending along the edge thereof and being formed with gaps into which said synthetic resin ring is molded so as to securely attach said synthetic resin ring to said circular center plate, said circular center plate further having a cylindrical portion proximate said periphery thereof, a stabilizing ring affixed to an outer surface of said cylindrical portion out of contact with said recording medium for providing rotational stability to said circular center plate, and a locating rib substantially concentric with said synthetic resin ring on said center plate and formed integrally with said upper half of the cartridge on the inside thereof and having a small diameter relative to said center plate and larger than the diameter of said synthetic resin ring so as to be located between said driving hole and said square center hole and having a height so as to depend around said synthetic resin ring for positioning said recording medium in said cartridge.