Erasing system for a magnetic recording and reproducing apparatus using a rotary magnetic medium

Claim 2

An erasing system for a magnetic recording and reproducing apparatus using a rotary magnetic medium comprising two magnetic heads held in contact with the rotary magnetic medium, means for rotating the magnetic medium at a predetermined velocity, means for stepping and intermittently transferring the two magnetic heads on the magnetic medium with certain stepping and stop intervals during a cycle of two fields of a video signal, means for alternately applying the video signal to the magnetic heads for alternately recording said signals in units of at least one field responsive to the stop interval of the magnetic head after it has been stepped by the stepping means, and means for applying an erasing current to each of the magnetic heads during the interval while the other head is recording and before the applying of the recording video signal to that same head during the stop interval of the magnetic heads, said stepping interval of said stepping means being substantially equal to or smaller than the vertical blanking interval of the video signal, the signals which have already been recorded on said magnetic medium being erased by the magnetic heads which have the erasing current applied thereto, and thereafter the video signal being recorded on the erased track by the same magnetic head.

Claim 3

An erasing system for a magnetic recording and reproducing apparatus using a rotary magnetic medium as defined in claim 1 wherein there are two of said magnetic heads, means whereby said stepping means drives both the magnetic heads alternately to step in a cycle comprising a unit of two fields or two frames, and each of said magnetic heads makes a stepping and an erasing for a first field or frame interval and a recording for a second field or frame interval.

Claim 4

An erasing system for a magnetic recording and reproducing apparatus using a rotary magnetic medium as defined in claim 2 wherein the magnetic heads supplied with the recording video signal make multiple recording on portions on the magnetic medium which remain unerased because the erasing current is not applied to the magnetic heads during approximately the stepping interval of the stepping means.

Claim 5

An erasing system for a magnetic recording and reproducing apparatus using a rotary magnetic medium as defined in claim 1 wherein said erasing current applying means applies the erasing current to the magnetic head during an interval extending substantially between the end of stepping of the stepping means and an end of at least one field interval extending after the start of the stepping process.

Claim 6

An erasing system for a magnetic recording and reproducing apparatus using a rotary magnetic medium as defined in claim 4 wherein the magnetic heads supplied with the recording video signal make multiple recordings on unerased portions which remain on the magnetic medium since the erasing current is not applied to the magnetic heads during approximately the stepping interval of the stepping means.

Claim 7

An erasing system for a magnetic recording and reproducing apparatus using a rotary magnetic medium as defined in claim 4 wherein the erasing current is applied to the magnetic heads during a period which starts slightly before the end of stepping by The stepping means.

Claim 8

An erasing system for a magnetic recording and reproducing apparatus using a rotary magnetic medium as defined in claim 1 further comprising means for generating a signal which is synchronized with rotation of the magnetic medium, means for taking out vertical synchronizing signals from the recording video signal, means for obtaining a switching signal jointly responsively to the rotation synchronizing signal and the vertical synchronizing signal, means responsive to the switching signal for generating a driving signal for driving the stepping means, means responsive to the switching signal for applying the erasing current to the magnetic heads for a predetermined interval, and further means responsive to the switching signal for switching the video signal and for feeding the switched video signal to the magnetic head, wherein said predetermined interval of the erasing current extends from substantially the end of stepping by the stepping means to the end of an interval, equal to the period of one field, beginning with the start of the stepping.

Claim 9

An erasing system for a magnetic recording and reproducing apparatus having a rotary magnetic medium comprising two magnetic heads in contact with the rotary magnetic medium, means for rotating the magnetic medium at a rate wherein one field of a video signal is recorded in each circular track on said medium, means for generating a first pulse series, each pulse of such video signal being synchronous in phase with each revolution of said rotary magnetic medium, first gating means for producing second and third pulse series responsive to a gating of alternate pulses from said first pulse series, said second and third pulse series being spaced apart from each other by a time interval equal to one field of the video signal, means responsive to said second and third pulse series for alternately and intermittently transferring the magnetic heads on the magnetic medium with predetermined stepping and stop intervals, means responsive to said second and third pulse series for producing two first series of square waves, the duration of each square wave being at least equal to said stepping interval and said square waves being spaced apart from each other by a time interval equal to one field of the video signal, means including first flip-flop circuits set by the trailing edges of each square wave of said two first square wave series and reset by said second and third pulse series for producing two second series of square waves which are spaced apart by a time interval equal to one field of the video signal, second gating means for gating an erasing current responsive to each pulse in said two second series of square waves respectively, means including a second flip-flop circuit set by said second pulse series and reset by said third pulse series for producing two third series of square waves which are spaced apart from each other by the time interval equal to one field of the video signal, switching means for switching the video signal responsive to each of said two third series of square waves respectively, and means for applying the output signals of said second gating means and said switching means to said two magnetic heads respectively, so that the video signal gated by said switching means follows immediately after the erasing current gated by said second gating means.

Claim 10

An erasing system for a magnetic recording and reproducing apparatus having a rotary magnetic medium comprising two magnetic heads in contact with the rotary magnetic medium, means for rotating the magnetic medium at a rate wherein one field of a video signal is recorded in each circular track on said medium, means for generating a first pulse series, each pulse of such video signal being synchronous in phase with each revolution of said rotary magnetic medium, first gating means for producing second and third pulse series responsive to a gating of alternate pulses from said first pulse series, said second and third pulse series being spaced apart from each other by a time interval equal to one field of the video signal, means responsive to said second and third pulse series for alternately and intermittently transferring the magnetic heads on the magnetic medium with predetermined stepping and stop intervals, means responsive to said second and third pulse series for producing two first series of square waves, the duration of each square wave being at least equal to said stepping interval and said square waves being spaced apart from each other by a time interval equal to one field of the video signal, means including first flip-flop circuits set by the trailing edges of each square wave of said two first square wave series and reset by said second and third pulse series for producing two second series of square waves which are spaced apart by a time interval equal to one field of the video signal, second gating means for gating an erasing current responsive to each pulse in said two second series of square waves respectively, means including a second flip-flop circuit set by said second pulse series and reset by said third pulse series for producing two third series of square waves which are spaced apart from each other by the time interval equal to one field of the video signal, switching means for switching the video signal responsive to each of said two third series of square waves respectively, and means for applying the output signals of said second gating means and said switching means to said two magnetic heads respectively, so that the video signal gated by said switching means follows immediately after the erasing current gated by said second gating means.

Claim 11

The erasing system as defined in claim 8 wherein said first gating means comprise synchronizing signal separator means for separating horizontal synchronizing pulses and vertical synchronizing pulses respectively from said video signal, means responsive to the horizontal and vertical synchronizing pulses for producing frame pulses, monostable multivibrator means operated responsive to the frame pulses for generating two square wave signals which have opposite polarities, and two AND gating means for gating said first pulse series responsive to each of the two square wave signals respectively and producing said second and third pulse serieS.