Dynamic magnetic information storage or retrieval – Miscellaneous
Patent
1979-08-06
1982-08-31
Konick, Bernard
Dynamic magnetic information storage or retrieval
Miscellaneous
360 742, 360 723, 360 963, 242 7551, 318 7, G11B 2710
Patent
active
043475388
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The position or setting of tapes in magnetic tape recorders can be determined by the counting of pulses which are derived from a part moving together with the magnetic tape such as, for example, the spindles. The number counted may be employed for indicating the tape setting. Since the length of the circumference of a tape reel varies with the coiling or uncoiling of the magnetic tapes this indication is not linear. That is, considerably varying values are obtained for the tape section assigned to individual counting steps as a function of the tape setting.
With a view towards improving the linearity of indication it has been proposed (German Auslegeschrift No. 24 16 060.9) to provide a scanning unit on each of the two spindles, to derive tape travelling pulses from the scanning units and to feed the sum of the pulses into a counter. While this method effects some improvement in indication it is in some cases still inadequate in effecting an improvement in linearity such as, for example, when the indication has to be calibrated to the length of tape which has been run dimensionally.
SUMMARY OF THE INVENTION
An object of the invention is to provide a method for indicating the tape setting which is greatly improved with respect to linearity as a result of which it becomes possible to perform an absolute calibration in meters or seconds.
In the course of the determination of the tape setting in a magnetic tape recorder by means of the counting of pulses derived typically from the take-up spindle; the changing reel diameters during the coiling operation produce a non-linear counting result over the tape length. In commercially available magnetic tape cassettes the length of play of a given cassette is a function of the tape length and different thickness tapes are used as a function of the tape length.
The invention is based on the finding that the variables affecting the winding operation which have to be allowed in the linearisation of the counting operation can be expressed by two values which can be easily determined during a test run of the magnetic tape recorder concerned. These are
1. The ratio of the diameter of the fully wound reel to the diameter of the empty hub of a reel and
2. The total number of turns (winding number) of a full reel.
One series of pulses each is derived from each of the two spindles for the detection of these values. The first value is determined by a frequency comparison of the pulse series during a test run from the starting setting of the magnetic tape at which the take-up reel is empty and the take-off reel is full. The second value is derived by a count of the pulses making up one of the pulse series over the full tape length or a part of the tape length. In the described embodiment the pulses are counted by the take-up spindle.
Assuming that the diameters of the hubs of the take-up and take-off reels are identical the tape setting can be derived with these values by means of the following formula ##EQU1##
The various symbols in this formula have the following meanings: L is the tape setting, a figure which varies linearly with the length of tape delivered which figure may be indicated (reported) through application of an appropriate factor in a length unit, for example meters, or in a timeunit such as minutes. D.sub.0 is the diameter of the hubs of the reels, N.sub.1 the appropriate number of turns on the take-up reel, N.sub.1ges the possible total number of turns, and a the frequency ratio of the pulse series derived from the take-up and take-off reels at the start of the winding process.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block circuit diagram of the invention.
FIGS. 2 and 3 are circuit units relating to the circuit of FIG. 1.
FIG. 4 is a variant of the circuit of FIG. 3.
FIG. 5 is an embodiment of a frequency comparator provided in the circuit of FIG. 2.
FIG. 6 is a table relating to the circuit of FIG. 5.
FIG. 7 shows pulse diagrams relating to the circuit of FIG. 5.
DESCRIPTION OF A PREFERRED EMBODIMENT
FIG. 1 shows part
REFERENCES:
patent: 3824694 (1974-07-01), Lesperance
patent: 4172231 (1979-10-01), Costemore et al.
Funkshau, 1975 vol. 47, No. 20, Scholz, Automatization of a Cassette Recorder.
Faber Alan
Konick Bernard
Licentia Patent-Verwaltungs-GmbH
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