Dynamic magnetic information storage or retrieval – Record transport with head moving during transducing – Tape record
Patent
1989-03-17
1991-11-19
Wolff, John H.
Dynamic magnetic information storage or retrieval
Record transport with head moving during transducing
Tape record
360 95, G11B 15665, G11B 1561
Patent
active
050670352
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a recording device such as a magnetic recording device with rotating head or heads with helical scanning.
PRIOR ART
The recording of data, whether analog or numerical, is almost always executed within a layer of very small thickness deposited on a support in the form of a flexible film. This is true for, e.g., writing on paper, photorecording and, above all, of the magnetic recording.
The analog magnetic recording of sound necessitates a relatively small speed between head and tape. On the other hand, since the signal
oise ratio of the recording is proportional to the utilized surface of the tape, the recording track has to be sufficiently wide. This is the reason why in the usual process, the tape moves in front of a stationary head.
For analog recording of a video signal or any numerical recording, the signal
oise ratio is less critical which permits the width of the recorded track to be greatly reduced. On the other hand, since the number of magnetic transitions per second is very high, one has to foresee a great relative speed between head and tape. For example, the professional analog recording of sound is generally executed at 19.05 or 38.1 cm/sec on a width of 2 to 6 mm, while the professional analog recording of a video signal (format C) is executed at a relative speed between head and tape of 25 m/sec but on a width of only 0.16 mm. Such a narrow tape moving at such a great speed is not practical. Therefore, since about 1950, the universally adopted solution for the recording of video signals in practice, makes use of mobile, rotatable heads which scan the surface of the magnetic tape.
Originally, this scanning was executed transversally, i.e., where the axis of rotation of the rotating head or scanner was parallel to the direction of the movement of the tape (format Quadruplex). Today, almost all new recording devices make use of helical scanning, i.e., where the tape moves helically about a cylinder, a portion of which is generally stationary and another portion of which is rotatable. This rotatable part comprises one or more magnetic heads which, due to the helical winding of the tape, scan the surface of the latter diagonally. The longitudinal component of the motion of the tape has the effect that the recorded tracks are not superimposed but that they are arranged like hatchings in a drawing.
In the devices actually known the tape is driven by the receiving coil of the tape and by a capstan in the form of a cylinder generally rotating at constant speed. Between these elements and the scanner, one finds various elements, like magnetic heads, provided for the auxiliary longitudinal tracks, a counting roll measuring the longitudinal path of the tape and various tape guides, among them the input and output guides of the scanner. These latter guides are generally stationary but in certain cases they can be rotatable (e.g., Ampex Nagra VPR 5).
The preceding shows that in all known cases there exists between the scanner and the capstan a relatively great length of tape. The rotation of the scanner, combined with the frictional effects in the guides, causes longitudinal vibrations in the tape which are only stopped by the capstan. These vibrations deteriorate the quality of the signal of the analog, as well as the numerical, recording.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the performances of the recorder.
The free length of the tape between the scanner and the capstan or capstans is greatly reduced if the capstan or capstans is/are provided in close proximity to the scanner. In this case, it is necessary to take measures for facilitating the loading of the tape. This is obtained by making the capstan displaceable in rails, such that it is capable of being shifted from one position where it engages the tape in the cartridge to a working position near the scanner. A variant of the invention aims to realize recordings at variable speed. In this case, it is necessary to correct the angle error of the tracks re
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Kudelski Stefan
Rosselet Ernest
Schlup Jean-Claude
Kudelski SA fabrique de'enregistreurs Nagra
Wolff John H.
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