Winding – tensioning – or guiding – Unwinding and rewinding a machine convertible information... – Automated stop or reverse
Reexamination Certificate
2000-03-07
2001-07-10
Marcelo, Emmanuel M. (Department: 3653)
Winding, tensioning, or guiding
Unwinding and rewinding a machine convertible information...
Automated stop or reverse
C360S074200
Reexamination Certificate
active
06257515
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus for recording and reproducing information on magnetic tape, more particularly to an improved method of detecting the end of the magnetic tape.
Magnetic tape is widely used for recording and reproducing audio and video signals. The operating modes of the recording and reproducing apparatus commonly include a fast-forward mode and a rewind mode, in which the tape is transported at high speed. In these high-speed modes, it is desirable to reduce the tape speed shortly before the end of the tape is reached, to lessen the shock that occurs when tape travel halts abruptly at the end of the tape. For this purpose, it is necessary to detect the approaching end of the tape.
A known detection method is to detect the rotational speeds or periods of the two reels on which the tape is wound, and monitor the ratio between the two speeds or periods. A disadvantage of this method is that it requires the simultaneous monitoring of the rotation of two reels, and repeated ratio calculations.
Some types of tape have a control track on which a control signal with a pulse waveform is recorded. The approaching end of the tape can then be detected by monitoring the number of control pulses per revolution of the supply reel. A disadvantage of this method is that it fails completely if the control signal is missing. Furthermore, even when the control signal is present, individual control pulses may be missing, or may not be picked up, causing the end of the tape to be detected at the wrong place.
SUMMARY OF THE INVENTION
An object of the present invention is to detect the approaching end of a magnetic tape reliably during high-speed tape transport, without having to monitor two separate rotational speeds or periods or calculate a ratio between them.
The invented magnetic recording and reproducing apparatus feeds magnetic tape from a supply reel to a take-up reel driven by a motor. A first sensor generates a first signal indicating each revolution of the supply reel. A second sensor generates a second signal responsive to the rotation of the motor. An end-of-tape detector counts the second signal with reference to the first signal, thereby determining the number of second signals occurring per revolution of the supply reel, and detects the approaching end of the magnetic tape from this number, by comparing the number with a threshold, for example.
To determine the threshold, the apparatus preferably has a third sensor that generates a third signal indicating each revolution of the take-up reel, and a classifier that counts the second signal with reference to the third signal, thereby determining the number of second signals occurring per revolution of the take-up reel.
The end of the tape is detected reliably because detection rests on sensing the revolution of a motor built into the apparatus, instead of sensing control pulses that may or may not be recorded on the tape. During the detection process, only the rotation of the supply reel is monitored, and no ratio calculation is necessary.
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Fukuda Kazunori
Ueo Kazuo
Marcelo Emmanuel M.
Mitsubishi Denki & Kabushiki Kaisha
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