Rotating magnetic head piezo-electric assembly and drive circuitry for video tape recorder

An apparatus for reproducing information signals recorded in a track extending obliquely on a magnetic tape and being preceded and followed by similar tracks which are parallel thereto and also have information signals recorded therein, with the tracks which are adjacent each other having the information signals recorded therein with magnetic domains at different angles in respect to the direction along the tracks;

• comprising a guide drum having said tape extending helically about at least a portion thereof while the tape is adapted to be longitudinally advanced, at least a portion of said drum being rotatable, a magnetic head adapted to scan along one of said tracks for reproducing the information signals recorded therein;
• head mounting means including piezo-electric means of elongated, plate-like configuration having opposed major surfaces with said head mounted at one end and the other end being cantilevered from said rotatable drum portion to rotate with the latter for causing said head to scan along the one of said tracks positioned in proximity thereto by advancement of the tape with torsional flexing of said piezo-electric means about its longitudinal median varying the azimuth angle of said head in respect to said track while longitudinal bending of said piezo-electric means is effective to deflect said head in a direction transverse to the length of the track, and pairs of first and second electrodes secured on said opposed major surfaces of the piezo-electric means and extending parallel to said longitudinal median with said first and second electrodes of one of said pairs being spaced laterally from said first and second electrodes, respectively, of the other of said pairs;
• and drive circuit means for applying selectively varied voltages across said first and second electrodes of said one pair and of said other pair, respectively, and thereby determining the position of said head both in respect to its azimuth angle and the deflection of the head in said transverse direction relative to said track, said drive circuit means including means connecting said first electrode of one of said pairs and said second electrode of the other of said pairs to ground, a source of a variable control voltage, means for providing a reversed polarity replica of said variable control voltage, means for providing each of said variable control voltage and said reversed polarity replica thereof with a selectively varied D.C. voltage bias, means for applying said variable control voltage with said D.C. voltage bias and said reversed polarity replica with said D.C. voltage bias to said second and first electrodes, respectively, of said one pair and said other pair, respectively, of the electrodes, means for determining said variable control voltage in dependence on the rotation of said head with said rotatable drum portion, and means for determining said D.C. voltage bias in dependence on the track being scanned by said head so as to make the azimuth angle of the latter correspond to the angle in respect to the direction along the scanned track of the magnetic domains with which the information signals are recorded in said scanned track.

In an apparatus of the type wherein signal information is recorded on a magnetic record medium in successive parallel tracks which are skewed with respect to a direction of travel of the record medium, said apparatus having a plurality of alternately operative magnetic heads which scan along said successive parallel tracks in order for the recording and normal reproducing of the signal information therein during travel of the record medium at a normal speed, with said magnetic heads having gaps at different azimuth angles, respectively, during recording, so that the signal information is recorded in adjacent tracks with magnetic domains at correspondingly different angles to the direction along the tracks, and in which slow motion reproducing of the recorded signal information is effected by causing said record medium to travel at a reduced speed with the result the tracks are scanned repeatedly by said heads;

• the improvement comprising head mounting means including, for each of said heads, piezo-electric means of elongated, plate-like configuration having opposed major surfaces with the respective head mounted at one end and the other end being cantilevered so that torsional flexing of said piezo-electric means about its longitudinal median varies the azimuth angle of the respective head in respect to the track being scanned thereby while longitudinal bending of said piezo-electric means is effective to deflect said respective head in a direction transverse to the length of the track being scanned, and pairs of first and second electrodes secured on said opposed major surfaces of the piezo-electric means and extending parallel to said longitudinal median with said first and second electrodes of one of said pairs being spaced laterally from the first and second electrodes, respectively, of the other of said pairs;
• and drive circuit means operative during said slow motion reproducing for applying selectively varied voltages across said first and second electrodes of said one pair and of said other pair, respectively, of each of said piezo-electric means so that the respective head, in scanning along one of said tracks, is deflected in said transverse direction for accurate scanning and has its azimuth angle determined to correspond to the angle of the magnetic domains recorded in said one track being scanned, said drive circuit means including, for each of the heads, means connecting said first electrode of one of said pairs and said second electrode of the other of said pairs to ground, a source of a variable control voltage, means for providing a reversed polarity replica of said variable control voltage, means for providing each of said variable control voltage and said reversed polarity replica thereof with a selectively varied D.C. voltage bias, means for applying said variable control voltage with said D.C. voltage bias and said reversed polarity replica with said D.C. voltage bias to said second and first electrodes, respectively, of said one pair and said other pair, respectively, of the electrodes on said piezo-electric means for each head, means for determining said variable control voltage in dependence on the rate of scanning movement of each said head, and means for determining said D.C. voltage bias in dependence on the track being scanned so as to make the azimuth angle of the head scanning such track correspond to the angle in respect to the direction along the scanned track of the magnetic domains with which the information signals are recorded in said scanned track.