1.  Field of the Invention
This invention relates to apparatus for recording and/or playing back information, particularly digital information, on magnetic tape packaged in the form of cassettes.  More specifically, the invention is directed to improvements in a magnetic tape cassette apparatus of the type having a magnetic head fixedly mounted on a pivotable cradle for receiving and holding a tape cassette. 
2.  Description of the Prior Art
Magnetic tape cassettes have recently found widespread usage as the input/output medium of digital information, and there are some digital tape cassette recorders or players that have won commercial acceptance.  Just like audio tape cassette players, digital cassette players usually comprise a cassette cradle pivotable between a loading position for receiving a tape cassette and a record-playback position for running the tape housed in the cassette with respect to a magnetic head for recording or playback.  A cassette locking mechanism is usually provided for locking and holding the tape cassette in the record-playback position of the cradle. 
In digital tape cassette apparatus of this type there are usually provided an electrical switch assembly for detecting the tape cassette as same is carried by the cradle to the record-playback position, another switch assembly for detecting one of a pair of breakable pawls provided to the cassette to prevent accidental erasure of a recording on the tape, and a cassette retainer spring or springs for biasing the tape cassette toward the magnetic head in the record-playback position of the cradle.  Usually, these switch assemblies and cassette retainer spring or springs have been mounted on stationary parts of the apparatus. 
This would give rise to no trouble if all the tape cassettes to be used with the apparatus were manufactured to exactly the same dimensional specifications.  Since in practice some variations in the size of tape cassettes are almost unavoidable, however, the switch assemblies and the cassette retainer spring or springs may not perform their intended functions in some instances.  Of course, they would function in the intended manner if their positions with respect to the under- or oversized tape cassettes were readjusted as required, but this would involve a highly troublesome procedure. 
Another disadvantage of the prior art concerns the cassette retainer spring or springs in particular.  Since the spring or springs are mounted on a stationary part of the apparatus so as to engage the tape cassette as same is carried to the record-playback position by the cradle, considerable resistance is thereby offered to the cradle movement, particularly from the record-playback to the loading position. 
Tape cassette players have been suggested wherein detector switch assemblies, a cassette locking mechanism and other means are moved to and away from their operating positions in step with the movement of the cradle between the loading and the record-playback positions.  These known devices are still unsatisfactory, however, especially in regard to smooth movement of the cradle between its two positions.