Patent GB-1483129-A (GB)
Title: Magnetic tape recording and/or playback machine
IPC: G11B15/665
Filed: 1975-01-09
Abstract: 1483129 Autothreading in helical-scan tape transports AMPEX CORP 9 Jan 1975 [19 Aug 1974] 974/75 Heading G5R A helical scan rotary head magnetic tape recording/playback apparatus for use with tape cassettes has means for applying vacuum suction to draw a loop of tape from the cassette 13, Fig. 2, and wrap it helically around a rotary head/tape guide drum assembly 21, means 171, Fig. 7, being provided for maintaining the two shanks of the tape loop separate from one another during recording/playback. Threading and recording/playback operations may be controlled manually or automatically by a programmed controller 43, Fig. 9. Autothreading is effected by energizing a vacuum pump (83), (84), Fig. 10 (not shown), to evacuate a chamber (26), Fig. 1 (not shown), around assembly 21 via ports 69 adjacent capstan 66, Fig. 2, and via ports 68 adjacent roller 67 whereby a tape loop is extracted from cassette 13. The loop may be pulled from cassette 13 entirely by vacuum with one reel braked by pivoting a plate 36 so that a drive wheel 34 of a motor (37), Fig. 3 (not shown), held at stop, engages driven wheel 31 or 32 of reel drive shaft 16 or 17, or motor (37) may be engaged to reverse drive take-up reel spindle 17 during loop formation. Plate 36 carries the reversible motor (37) and has a cam follower pin 46 engaging in a slot 48 of a cam (47), Fig. 3. When solenoids 56 (57) are both de-energized cam (47) is in a neutral position with neither of wheels 31, 32 engaged with wheel 34, energization of solenoid 56 or (57) moving cam (47) downwards or upwards to drive take-up shaft 17 or supply shaft 16 respectively. As the loop lengthens to position 74, Fig. 2, it engages the wall of the chamber (26) at erase head 22 to divide the chamber in two, one part evacuated by ports 68 and the other part evacuated by ports 69 to a lesser extent due to venting to atmosphere via ports 24 whereby the tape loop first encompasses the operative position of a retracted idler 63 and then one shank of the loop rolls, without friction, on to drum 21 while the other shank slides along the outer wall of chamber (26) being held thereat by vacuum applied to ports 77, 78, 79, Fig. 7 (80), Fig. 11 (not shown), in that wall. When the tape loop reaches capstan 66, substantially all the atmospheric air is cut off from the vacuum system giving a pressure drop sensed by a pressure sensitive switch (81), Fig. 10, causing tape feed by motor 37 to stop. A motor (118), Fig. 4 (not shown), then drives a shaft 119, Fig. 9, a belt 126 coupled to a bracket 129 carrying idler roller 63, and a belt (146), Fig. 5 (not shown), coupled to a bracket (151), Figs. 11 to 13 (not shown), carrying capstan pinch roller 64, whereby rollers 63, 64 are raised from retracted positions to standby positions within the tape loop and spaced from idler 67 and capstan 66, respectively, solenoids 141, Fig. 9 (161), Fig. 5, being then operable to engage rollers 63, 64 with idler 67 and capstan 66, respectively. Motor 118 also operates to raise a curved guide 171, Fig. 2, into the tape loop to engage and guide the return shank of the loop when the vacuum pump (83), (84) is de-energized in response to a microswitch (158), Figs. 11-13, sensing that rollers 63, 64 and guide 171 are in their raised positions. The positions of capstan 66 and roller 64 may be interchanged or a vacuum capstan may be provided in alternative embodiments. The cassette 13 may be held in a plane perpendicular to the axis of drum 21, Figs. 14A, 14B (not shown), or in a plane at an angle α, equal to the helical pitch angle of the tape around drum 21, to such a perpendicular plane, Figs. 15A, 15B (not shown). The top part 193, Fig. 7, of drum 21 carries the heads 140a( 140b) and is rotated via a belt (191) by a motor (188), Fig. 6 (not shown), and capstan 66, adjacent which is a longitudinaltrack head 208, Figs. 2, 7, is rotated via a belt (196) by a motor (197), Fig. 5. The tape section around drum 21 is tensioned by means of the retractable idler 63 pressing against the idler 67 which is acted on by a brake (204), (206), Fig. 4. Tape unloading may be effected in response to head 208 sensing a signal at the end of the tape or of a recorded section causing controller 43 to stop drive of the capstan 66 and tape reels, un-pinch the rollers 63, 64, and then retract rollers 63, 64 and guide 171 using motor (118). When a microswitch (164), Figs. 11 to 13, senses rollers 63, 64 and guide 171 are at their retracted positions, controller 43 stops motor (118) and energizes solenoid (57), Fig. 3 and motor (37) to rewind the tape loop, and then the tape on the take-up reel, on to the supply reel until controller 43 receives a beginning-of-tape signal from a photoelectric sensor (not shown).