Patent ID: 7097126

Claim:
A magnetic tape cartridge, for rotatably housing within a cartridge case a single reel having magnetic tape wound thereon, comprising reel-rotation restraining means for allowing rotation of said reel when being used and restricting said rotation when not being used; wherein said reel-rotation restraining means has a restraining member for restricting rotation of said reel by moving toward or away from said reel, an urging member for urging said restraining member in a restraining direction, and a releasing member for moving said restraining member in a releasing direction, by rotating integrally with said reel and moving according to a chucking operation of drive-side rotation drive means; said reel is provided with a reel gear which meshes with a driving gear of said drive-side rotation drive means, and a pushing-up portion formed in part of said releasing member is provided so that a distal end thereof can abut said-driving gear through a through hole provided in said reel gear; and said reel is formed by molding a metal reel plate by insert molding, and said reel is also formed so that outside the outer peripheral surface of said reel plate, a clearance in the form of a circumferential groove is formed between said outer peripheral surface and a bottom wall of said reel, and so that outside said clearance, said reel gear is formed.