Magnetic tape cartridge with brake release push rod extending through reel hole wider than only one reel gear pitch

1. A magnetic tape cartridge comprising a cartridge casing, a single reel around which a magnetic tape is wound and which is contained in the cartridge casing for rotation, and a brake means which is movable between an operative position where it prevents rotation of the reel and a retracted position where it permits rotation of the reel,

wherein

the brake means comprises a brake member which is movable between an operative position where it engages with the reel to prevent rotation of the reel and a retracted position where it is disengaged from the reel to permit rotation of the reel, an urging means which urges the brake member toward the operative position, and a brake release member which is disposed in the cartridge casing to be rotated together with the reel and moves the brake member to the retracted position in response to chucking operation of a tape drive mechanism of a tape drive system,

the reel is provided with a reel gear which is brought into mesh with a drive gear of the tape drive mechanism and a through hole through which a push rod extending from the brake release member projects to be brought into abutment against the drive gear of the tape drive mechanism so that the brake release member moves the brake member to the retracted position, and

the through hole opens in an area which is wider than tips of teeth of the reel gear and narrower than two times a pitch of the reel gear, the area including at least a pair of opposed flanks of the reel gear which form a valley of the reel gear.

2. The magnetic tape cartridge as defined in claim 1 , in which the through hole opens beyond the tips of adjacent teeth of the reel gear.

3. The magnetic tape cartridge as defined in claim 1 , wherein at least one of the brake release member and the brake member is formed of synthetic resin containing therein lubricant selected from the group consisting of molybdenum, polytetrafluoroethylene, graphite, potassium titanate whisker, and silicone formed of dimethyl polysiloxane.

4. The magnetic tape cartridge as defined in claim 1 , wherein the brake release member is formed of fiber reinforced resin, and said fiber reinforced resin is one of long-fiber reinforced resin and carbon fiber reinforced resin.

5. The magnetic tape cartridge as defined in claim 1 , wherein when the push rod is moved to be brought into abutment against the drive gear, the push rod is not coincidental with the tips of the teeth of the reel gear.