Patent GB-1062910-A (GB)
Title: Improvements in or relating to tape recording and playback machines
IPC: G11B15/16
Filed: 1965-04-09
Abstract: 1,062,910. Magnetic recording and playback. AMPEX CORPORATION. April 9, 1965 [May 4, 1964], No. 15081/65. Heading G5R. A tape feeding mechanism for use e.g. in a stereo tape recorder which is designed to record and playback tape moving in both forward and reverse longitudinal directions between a pair of reels includes a main drive operable in both forward and reverse directions, arrangements for selectively uncoupling the main drive with the tape and with the take-up reel for the tape, there being a lost motion connection between the tape drive and the-reel drive so that the drive to the reel operates when the tape is driven and may also operate independently, and a reel brake arrangement which operates so as to continuously brake at least the supply reel. Play-record operation.-With the machine switched on power is supplied to a motor 101 which by means of a shaft bearing a number of different diameter pulleys drives a belt around flywheels 113 and 114 attached to drive capstans 61 and 62. The drive is applied in such a direction that the belt travels from the motor to the upstream capstan and then the downstream capstan, and the downstream capstan tends to rotate faster than the upstream so that the tape is held in tension between the two. To play, a knob attached to a play slide 151 is operated, to cause fingers 184 on the slide to rotate pinch rollers into engagement with the drive capstans. The drive to the take-up reel is applied by one of drive pulleys 123 or 124 (depending on the direction of movement of the tape), which are supported at the ends of a pivoted arm 126 and driven by a second belt 128 which passes around a further pulley on the motor shaft, around the drive pulleys and also around an idler 129. The operation of the playslide 151 also causes a wind slide 201 to be moved, to operate a brake slide 241 which applies a braking force to the supply reel. Furthermore, operation of the slide 151 causes a plate 148 to pivot about bearings 149 so as to move a drive wheel on the shaft of the take-up reel against a spring to engage a driving wheel on the appropriate pulley 123, 124, the relative actions of the wheels being appropriate to the play record operation. The movement of the wind slide 201 releases the arm 126 from its locked position so that it swings over to enable the appropriate driving wheel to engage the take-up reel. The movement of the plate 126 operates switches in the electronic circuitry of the recorder. Fast wind operation.-A mechanical interlock between the relevant control knobs prevents both fast wind and record being operated simultaneously. When the fast wind control is operated the wind slide 201 is pushed to its limit so that minimum braking is applied to the supply reel. The play slide 151 is not operated and held in the stop position, and the tape is held positively away from the drive capstan by means of pins 196, 197 on the play slide. Furthermore, the plate 148 is not pivoted, and a different pair of wheels on the reel spindles and drive pulley spindle engage so as to provide rapid rotation of the take-up reel. Supply reel brake.-As mentioned above, the movement of the wind slide 201 operates a brake slide 241. This slide is carried over by the rotation of the take-up reel to bear on the supply reel. A spring on its other side engages with a rotating wheel 242 or 243. The relative positions of the spring and the wheel control the braking force applied to the supply reel, and these positions are variable in accordance with the position of the play slide, which controls the extent to which the slide 241 can move by means of parts engaging projections on the slide 241. Speed changing in the play record mode is effected by altering the position of a lever coupled to a pair of fingers which engage the belt 112 and move it on to a different size drive pulley at the motor shaft. The fingers are mounted one on each side of the drive pulleys and are rotatable, and take up positions depending on the direction of rotation of the belt. A mechanism is provided for sensing the end of the tape, and includes an arm normally held in tension against a spring by the tape, which swings over to close switch contacts when the end of the tape or a break in the tape passes it; the switch being used to switch off the machine. Tape guides are provided, positioned close to the drive capstans and consist of rods around which the tape bends, with edge guiding flanges fitted at right angles to the rod direction to define the correct tape alignment. The recorder may be provided with four heads, one pair for erasing and play or record on forward drive, using tracks 1 and 3 of a four-track tape, another for use on reverse drive using tracks 2 and 4. The erase head for reverse drive may be omitted where it is only required to play back prerecorded tapes. An arrangement is provided for generating a 20 c/s. signal which may be recorded at the end of the tape tracks. When this signal is detected at a playback head, it is used to switch off or reverse the recorder. Suitable relay circuitry is described to enable the electrical functions for the system to be performed. The directions in which the recorder operates is controlled by a mechanical mechanism which actuates a switch to control the direction of operation of the motor 101. The mechanism operates in association with a solenoid which ensures that the recorder is always returned to the forward direction when switched off. The mechanism is also interlocked with the fast wind mechanism to prevent its use during a fast wind operation.