1. Field of the Invention
This invention relates generally to a leader for a magnetic or other recording tape, and more particularly is directed to an improved leader for a magnetic or other recording tape which, when secured to one or both of the ends of the latter, may be detected to indicate the presence of the adjacent end of the recording tape in an audio or video recording and/or reproducing apparatus or the like.
2. Description of the Prior Art
In tape cassettes for use in audio or video recording and/or reproducing apparatus, it is known to provide leaders connected between the opposite ends of a magnetic recording tape and the hubs of the supply and takeup reels on which the tape is wound so that one or the other of the tape leaders can be detected to indicate the full unwinding of the tape from a respective reel during a recording, reproducing, fast-forward or rewind operation of the apparatus in which the tape cassette is employed. One existing type of tape leader is formed of a flexible base of polyester film having a thin layer or film of aluminum or copper provided on one surface of the base, as by vapor depositing or plating the metal on the base or by adhering or bonding a metal film to the base. A tape leader of the foregoing type can be conveniently detected by a resonance sensor including an oscillator having a L-C resonance circuit, a detector for detecting the output of the oscillator, and a warning and/or shut-off mechanism which responds to detection of a change in the frequency of the oscillator output or a halt in such output. At least the inductance element of the L-C resonance circuit is included in a sensor which is disposed adjacent the path of the recording tape so that, when the tape leader with an aluminum or copper film or coating thereon is disposed adjacent the sensor, the inductance or sharpness of the resonance circuit is changed or decreased and, accordingly, the oscillating frequency is changed or the oscillation is halted. For example, in an existing video tape recorder (VTR), when the tape leader is detected, as aforesaid, an automatic shut-off mechanism is actuated or energized to halt the recording, reproducing, fast-forward or rewinding operation and to eject the tape cassette from the VTR. Further, in such VTR, detection of the tape leader causes energizing of a warning lamp and/or buzzer or other audible signal.
However, the existing tape leader, as described above, has a relatively poor ability to return to its original flat condition after being bent. Therefore, after frequent use of the recording tape having such leader or leaders, the latter may become crumpled or snap, or cracks or fissures may develop in the conductive metal film or coating thereof. The foregoing problems are especially encountered when the recording tape with a leader or leaders is made to follow a sinuous path about numerous tape guides in the tape cassette and/or in the recording and/or reproducing apparatus with which the cassette is used. When a tape leader is damaged, as aforesaid, it is difficult to replace the same, particularly if the associated recording tape and leaders are incorporated in a tape cassette. Furthermore, when the tape leader or leaders become crumpled, the crumpled condition of the leader material may injure or cause uneven winding of the magnetic or other recording tape about the crumpled leader on the associated supply or takeup reel with the result that dropout of the video or other recorded signals may be experienced.
Moreover, in the above described existing tape leader, the aluminum or copper film is corroded or oxidized when the recording tape is exposed to a humid atmosphere for an extended length of time. Such corrosion or oxidation of the aluminum or copper film of the tape leader changes its electric conductivity, with the result that the sensing of the tape-end is undesirably influenced, that is, the sensor can no longer reliably detect the tape leader when the latter is adjacent thereto.