A tape cartridge having a leader block provided therein has been used for some magnetic recording and reproducing apparatuses which are provided as a peripheral equipment for a computer to back up information and are adapted to use a tape cartridge having a magnetic tape wound on a single reel in the tape cartridge and guided along a predetermined guide path to a winding reel in the apparatus. Such a tape cartridge has a leader block provided at a leading end of the magnetic tape while the apparatus has a drawing pin member associated with the leader block.
Such a drawing pin member is disclosed in Japanese Patent Application Publication No. 13,097/1984, for example. In this prior art, the drawing pin member is in the form of a cylinder and is formed of a relatively thinner cylindrical portion and an enlarged portion provided at the leading end of the thinner cylindrical portion. The drawing pin member is engaged with a slot in the leader block including a recess provided corresponding to the enlarged portion.
In order to bring the tape cartridge to an operative position, it is inserted into a cartridge holder at a loading/unloading position, which causes the slot in the leader block to be engaged with the cylindrical portion of the drawing pin member. Then, the tape cartridge is pushed down to the operative position, which causes the recess of the slot to be engaged with the enlarged portion of the drawing pin member so as to connect the leader block to the drawing pin member.
In such an apparatus as constructed to manually move the tape cartridge to the operative position after it is inserted into the cartridge holder at its loading/unloading position, the tape cartridge tends to be inserted into the cartridge holder while the cartridge holder is being pushed down toward the operative position. In this case, the enlarged portion of the drawing pin member engages the slot in the leader block, but the drawing pin member is never inserted into the slot because the enlarged portion has a size larger than that of the slot and therefore is pushed in a direction in which the tape cartridge is inserted.
In general, the drawing pin member is driven by an electric motor, but if no worm gears are provided in a reduction mechansim for reducing the revolution speed of the electric motor, then the drawing pin member is moved by the pushing force thereof. In this condition, the leader block can be no longer engaged with the drawing pin member. Thus, the electric source to the motor is required to be interrupted in order to return the original condition of the drawing pin member.