Patent GB-1456783-A (GB)
Title: Video magnetic tape apparatus
IPC: G11B15/665
Filed: 1974-07-17
Abstract: 1456783 Video tape apparatus SONY CORP 17 July 1974 [9 Aug 1973] 31694/74 Heading G5R Video magnetic tape apparatus has a rotary head drum 38, Fig. 1, an automatic tape loading arrangement operative to load a video magnetic tape in a first position in which a tape loop is wrapped around a portion of drum 38 for recording and playback operations and operative to load the tape in a second position in which a tape loop is wrapped around drum 38 for fast tape transport operations, the tape loop in the second position being shorter than the loop in the first and engaging a shorter portion of drum 38 than in the first position, timing pulse transducing means arranged to replay synchronizing pulses from the tape when loaded in the second position, and a counter for counting said pulses from the timing pulse transducing means. Tape loading from a cassette 11, Fig. 1, is effected by pivoting arms 27, 29, carrying guide pins 24, 26, from the dotted to operative fullline positions, and by rotating a ring 42 from a position in which a guide 43 and a pinch roller 48 thereon are located between run T 1  of the tape and a wall 23 of the cassette, to the full-line position of Fig. 1, whereby the tape extends from the cassette around guides 14, 34, past erase head 36, around guides 26, 37, head drum 38, guide 58, control pulse head 59, audio head 61, guide 62 and initially around guide 43 until solenoid-operated member 66 moves pinch roller 48 to engage capstan 67 to drive the tape back around guides 51, 49, 24, 39 to cassette 11. During fast forward and rewind modes the tape is arranged in a short loop path from guide 34 past head 36, guides 26, 37, a short length of the periphery of drum 38 and then directly along path T 3  to guide 24 and thence via guide 39 to cassette 11. The erase head 36 extends across the full width of the tape and can be used during playback, fast wind or rewind to pick up timing pulses recorded on the lower edge of the tape by head 59. The head 36 may have a main erase section (118), Fig. 5 (not shown), extending across the video and audio track sections of the tape and a narrower section (122) operable to replay or erase on the timing pulse track section. The counting circuitry. Fig. 3, has a sync. separator 88 and monostable 89 acting to derive timing pulse signals at the frame rate from the complex video signal at input 75, the timing pulse signals passing via switch 92 to head 59 for recording and also passing via differentiator 91, rectifier 96 and switch 99 to up/down counter 101, driver 102 and indicator 103 in the record mode position of switch 99. During rewind, fast wind and playback the recorded timing pulses picked up and differentiated by head 36 pass to counter 101 via amplifier 94 and rectifier 98. Alternatively, during playback, head 59 may supply replayed timing pulses to counter 101. In alternative circuitry, Fig. 6 (not shown), the counter receives timing pulses picked up by a transducer (128) responsive to a magnet 84 on the shaft 82 of video head motor 83 during record and playback, and head 36, or alternatively a separate head (132) adjacent thereto, plays back timing pulses to counter 101 during rewind, fast wind and, if required, during playback. The indicator 103 may indicate elapsed time and/or the number of pulses counted, e.g. it may indicate minutes, seconds and tenths of a second, or hours, minutes, seconds and the number of video fields of the current second.